BULLETIN OF THE FLORIDA STATE MUSEUM BIOLOGICAL SCIENCES Volume 4 Number I A TABULAR SUMMARY OF THE BIOLOGY OF NORTH AMERICAN MAYFLY NYMPHS (EPHEMEROPTERA) Lewis Berner PLUS 0 UNIVERSITY OF FLORIDA Gainesville 1959 The numbers of THE BULLETIN OF THE FLORIDA STATE MUSEUM, BIOLOGICAL SCIENCES, will be published at irregular intervals. Volumes will contain about 800 pages and will not necessarily be completed in any one calendar year. OLIVER L. 'AUSTIN, JR,, Editor The publication of this number of THE BUL- LETIN has been made possible by a grant from the Graduate School, University of Florida. All communications cbncerning purchase or exchange of the publication sh6uld be addressed to the Curator of Biological Sciences, Florida State Museum, Seagle Building, Gainesville, Florida. Manuscripts should be sent to the Editor of the BULLETIN, Flint Hall, University of Florida, Gainesville, Florida. Published 28 April 1959 Price for this issue $1.85 A TABULAR SUMMARY OF THE BIOLOGY OF NORTH AMERICAN MAYFLY NYMPHS (EPHEMEROPTERA)1 LEWIS BERNER 2 At the request of the Director of the Committee on the "Handbo,ok of Biological Data", National Research Council, I compiled a sum- mary of the biology of immature mayflies in tabular form. These tables were to have been a part of a larger compilation, "A Handbook of Aquatic Biology. However, the editors, after examining the con- ttibutions from many sources, reluctantly concluded that. a suitable and adequate basis for a useful handbook on aquatic biology was lacking and cancelled plans for publication. Inasmuch as these tables rdpresent the first compilation of this sort for mayfly nymphs, it was my feeling that they should be published for the use of biologists and students, even though the projected larger work will not appear. The geographic divisions were chosen rather arbitrarily as a matter of convenience.3 All columns should be checked for distribu- tion as some species may be listed for two or more geographic sec- tiens: No Mexican species are included as the data on the ephemerop- teran fauna of this area are too fragmentary. - 1 The preparation of this paper was supported in part by Research Grant No. RG-4058 from the National Institutes of Health, Public Health Service. 2 The author is Professor of Biological Sciences at the University of Florida, Gainesville. He is also a Research Associate of the Florida State Museum. - Manuscript received 21 May 1958.-ED. 9 This footnote applies to all tables. The United States is divided into geo- graphic areas as follows: Northeast: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Con- necticut, New York, New Jersey, Pennsylvania, Maryland, Delaware, Virginia (in part), West Virginia. Southeast: North Car6lina, South Carolina, Tennessee, Mississippi, Louisiana, Alabama, Georgia, Florida, Virginia (in part). Central: Ohio, Kentucky, Michigan, Indiana, Wisconsin, Illinois, Arkansas, Mis- souri, .Iowa, Minnesota, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas. Southwest: Cblorado, New Mexico, ·Utah, Arizona, Nevada, California. Northwest: Washingt6n, Oregon, Idaho, Montana, Wyoming. Canada is subdivided as follows: East: Newfoundland, Nova Scotia, New Brunswick, Labrador, Quebec, Eastern Ontario. Central: Western Ontario, Manitoba, Saskatchewan. - West: Alberta and British C61umbia. 2 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Only previously published records are included in the tabulation. The column headed "characteristics of nymphs" lists major generic characteristics and references to readily available illustrations. The column on taxonomy includes the publication in which the genus was described, the name of the type species, and the type locality. Complete citations for most gendic descriptions can be found in Edmunds and Allen (1957). As this paper is meant to be a summary of the bidlogy of mayfly immatures, I do not believe that it is pertinent to include a key. Several good one5 are available, the most recent being those of Day (1956), Pennak (1958), and Burks (1953). These keys include all except the most recent modifications in the systematics of the Ephemeroptera. FAMILIES AND GENERA OF NORTH AMERICAN MAYFLIES NORTH OF MExICO 4.5 Superfamily Heptagenioidea Subfamily Anepeorinae Family Siphlonuridae Anepeorus MeDunnough Subfamily Siphlonurinae Subfamily Pse-udironinae Acanthametropus Tshernova Pseudiron MeDunnough Ameletus Eat6n Family Ametropodidae Edmundsius Day Subfamily Ametropodinae Paramel€tus Bengtsson Ametropus Albarda Siphlonisca Needham Subfamily Metretopodinae Siphlonurus Eaton Metretopus Eaton Subfamily Isonychiinae Siphloplecton Clemens Isongchia Eaton Family Baetidae Family Oligoneuriidae Subfamily Baetinae Subfamily Oligoneuriinae Apobaetis Day Homoeoneuria Eaton Baetis Leach Lachlania Hagen Baetodes Needham and Murphy Family Heptageniidae Callibaetis Eaton Subfamily Heptageniinae Centroptilum Eatoh Arthroplea Bengtsson Cloeon Leach Cinggma Eaton Neocloeon Traver Cinygmula MeDunnough Paracloeodes Day Epeorus. Eaton Pseudocloeon Klapalek Heptagenia Walsh Superfamily Leptophlebioidea Rhithrogena Eaton Family Leptophlebiidae Stenonema Traver ' Phylogenetic arrangement that of Edmunds and Allen (1957). 5'Georges Demoulin (1958) published a new classification of higher categories after my manuscript had gone to press. The citation is as follows: Nouveau schema de classification des Archodonates et des Ephdmdroptdres. Inst. Roy. des Sci. Natur. de Belg., Bull. XXXIY (27): 1-19. 1959 BERNER: NORTH, AMERICAN MAYFLY NYMPHS 8 Subfamily Leptophlebiinae Neoephemera MeDunnough Choroterpes Eaton Superfamily Ephemeroidea Habrophlebia Eaton. Fam,ily Potamanthidae Habrophlebiodes Ulmer Subfamily Potamanthinae Leptophlebia Westwood Potomanthus Pictet Paraleptophlebia Lestage Family Behningiidae Thraulodes Ulmer Dolania Edmunds and Traver Traverella Edmunds Family Ephemeridae Family Ephemerellidae Subfamily Ephemerinae Subfamily Ephemerellinae Ephemera Linnaeus Ephemerella Walsh · Hexagenia Walsh Family Tricorythidae Pentagenia Walsh Subfamily Leptohyphinae Family Polymitarcidae Leptohyphes Eaton Subfamily Polymitarcinae Tricorythodes Ulmer Ephoron Williamson Superfamily Caenoidea Subfamily Campsurinae Family Caenidae Campsurus Eaton Subfamily Caeninae Tortopus Needham and Murphy Brach!/tercus Curtis Superfamily Prosopistomatoidea Caenis Stephens Family Baetiscidae Family Neoephemeridae Subfamily Baetiscinae Subfamily Neoephemerinae Baetisca Walsh ,4 BULLETIN FLORIDA STATE MUSEUM Vol. 4 ACANTHAMETROPUS TSHERNOVA United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. pecatonica (Burks) OOXOO 0 0 0 Characteristics Body streamlined. Head rounded, eyes lateral; a pair of short, of Nymphs submedian horns near the antennal bases. A pair of projecting, finger-like lobes on the lateral margins of pro- and mesonotum. A hook4ike projection on each segment of thoracic sternum, and a median, dorsal, hook-like spur on each abdominal segment. Claws long and slender. Abdominal segments. with a pair of adute projections at postero-lateral angles; 7 pairs of deeply fissured .gills, each gill consisting of a dorsal member with a recurved, ventral flap and another ventral member. Three short caudal filaments. Body length 20 mm. or more. Illustration: Burks, 1958, fig. 812. Habitat of Rapid, shallow, moderate-sized streams with sand and rock Nymphs bottoms. Apparently very rare as only a single specimen has been taken in North America. Life History Unknown. Taxonomy Tshernova, 1948. Dokladi Ak. Nauk. N. S. 60(8): 1458. Type species: A. nikolskui Tshernova; type locality: Transbaikal, Amur Basin. AMELETUS EATON , United States Canada Species S.E. N.E, C. S.W. N.W. E. C. W. aequivocus MeDunnough 0 0 X 0 alticolus MeDunnough O 0 0 0 amador Mayo 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 browni MeDunnough o x ceter MeDunnough 0 0 0 0 > < 0 0 0 0 0 0 > < 0 > < . % 0 0 0 0 0 0 0 O O K celeroides MeDunnaugh o . 0 connectus MeDunnough o o connectina McDunnough 0 0 cooki McDunnough 0 0 0 0 0 0 0 0 0 0 0 0 . 0 0 X X 0 * 0 0 > 1 X X X 0 0 0 0 0 0 0 0 dissitus Eaton 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 % exquisitus Eaton o x o facilis Day 0 0 0 falsus Mebunnough 0 0 0 imbellis Day 0 0 6 lineatus Traver x 0 0 ludens Needham 0 0 0 0 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS . 5 United States Canada Species S.E. N.E. C. S.W. N.W. monta Mayo 0 0 0 0 oregonensis Eaton 0- 0 X querulus MeDunnough 0 0 W 0 0 0 0 ,0 0 0 'e x c o o o c 0 , 0 0 0 0 0 0 ~ X X X 'C X X X K shepherdi Traver 0 0 simmor MODunnough 0 0 Sparsatus MoDunnough ' o x 0 , 0 0 0 0 0 0 6 , 0 0 0 0 0 0 0 0 0 0 0 0 0 subnotatus Eaton x 0 0 su#usus MeDunnough 0 0 0 tertius MODunnough , 0 0 0 0 tuberculatus McDunnough O 0 OX O X O C O O O C K O K O ualidus McDunnough 0 0 0 X cancouverensis MeDunnough 000 0 OX velox Dodds 0 0 x 0 0 x vernalis MeDunnough 000 0 OX Characteristics B6dy streamlined. Head rdunded, eyes lateral; maxilla with of Nymphs broad crown bearing many long, pectinate spines. Prominent spines usually present at postero-lateral angles of abdominal segment5 4-9. Seven pairs Of platelike, gills; single, oval, and small. Three caudal filaments, usually with a wide, dark, trans- verse band at middle and narrow, dark band at· apex. Body length: 8-14 mm. Illustration: Day, 1956, fig. 8: 1. Habitat of Usually found in small, rapidly flowing streams where they live Nymphs among pebbles or at banks, attached to vegetation or debris. Have been found in streams at' altitudes as high as 11,000 -feet., Sometimes found in lakes and ponds with clean rock or gravel bottoms, Habits of Strong swimmers; will swim in water flowing at rate of 2 to 3 Nymphs fe*t per second, but seek quieter water before coming to rest on bottom. Life' History Probably takes one year to develop from egg to adult. Number of instars unknown. One speciek, A. tudens, demonstrated to be parthenogenetic. Emerges as early as February in southeast to August in Canada. Nymph leaves water to emerge. Eggs laid few at time, scattered. Eggs of some species laid in streams which become dry during part of year and can withstand dessi- cation; eggs hatch after stream flow recommences. Taxon6my Eaton, 1885. Trans. Linn. Soc: London. 2nd Ser. 8.210. Type species: A. subnotatus Eaton, type locality: Colorado. 6 BULLETIN FLORIDA STATE MUSEUM Vol. 4 AMETROPUS ALBARDA United States Canada Species S.E. N.E. C. S.W.. N.W. E. C. W. atbrighti Traver O O O X O 000 neavei MeDunnough 0 0 0 0 0 O 0 X Characteristics Body streamlined. Head rounded; eyes iateral; head very small; of Nymphs frontal margin. cut away on each side almost to bases of antennae ' so that mouthparts are almost entirely exposed. Membranous flap extends upward and backward from posterior margin of the prosternum. Membranous appendage attached to inner margin of fore coxa; apical porti6n densely c16thed with hairs; legs slender, fore leg sh6rtest. Tarsal claw of fore· leg slender and slightly curved, bearing 4 or 5 long spines; similar spines on tarsus and tibia. Claws of middle and hind legs longer and straighter, 6ach fully as long as tarsus and about twice length of tibia. Flattened lateral extensions on abdominal segments 2-9, with short postero-lateral spines on segments 8 and 9. Gills single, obovate. Three caudal filaments; median filament with heavy fringe of hairs on' both sides, laterals heavily fringed on inner margins. Maximum body length at least 17 min. Illustra-, tion: Needham, Traver and Hsu, 1985, pl. XXXV. Habitat 6f In streams, on bottom amid rocks and sand. Only nymphs re- Nymphs corded from North America taken at altitude of _5400 feet. Life History Unknown. An adult taken in July. Taxonomy Albarda, 1878. Ent. Mo. Mag. 15: 129. Type species: A. fragilis Albarda; type locality: Arnh6m, Holland. ANEPEORUS McDUNNOUGH United State5 Canada Species S.E. N.E. C. S.W. N.W. E. C. W. rusticw MeDunnough 000XO 000 simplex (Wa15h) x o x 0 0 0 0 0 Characteristics Body flattened. .Head flattened; eyes dorsal, located near pos- of Nymphs terior margin of head; mouthparts those of predator; mandibles with long, slender incisors, molar surfaces absent. Legs Rat- tened; dense fringe of long hairs along posterior margins or femora and middle and hind tibae; claws long and slender. Abdomen flattened dorso-ventrally and broad; tergites covered with dense, woolly hairs. Gills ventral, composed of numerous filaments radialjng out from a central plate. Three caudal Ela- ments of approximately equal length. Caudal filaments rela- 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 7 tively bare. Body length: probably 6-8 mm. Illustration: Burks, 1953, fig. 394. Habitat of Unknown. Nymphs Habits of Unknown. Nymphs Life History Unknown. Adults have been. collected June, July, and Sep- tember. Taxonomy McDunnough, 1925. Can. Ent. 57: 190. Type species: A. rusticus MODunnough; type locality: Saskatoon, Saskatchewan. APOBAETIS DAY United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. indeprensus Day 0 0 0 X O 0-00 Characteristics Body rounded; head rounded; eyes lateral; labrum with a of Nymphs straight, unmodified anterior margin; labial palp with 2 seg- ments, distal margin of terminal segment squarely truncate and set with stiff spines, a sharp and V-shaped slot on innBr apical margin. Tarsal claws of all legs very long and Bne, fully as long as tarsus, almost straight, and without denticles. Gilts ovate and single. Three caudal filaments; median filament Often as long as laterals: Middle Elamentheavily margined with fine hairs on each side, and lateral filaments heavily margined with hairs on medial side.·Body length: 4 mm. Illustration: not illustrated in full; parts in Day, 1955, figs. 1-6., Habitat of Warm-water species from a river which has been dredged, di- Nymphs verted, dammed, and partially polluted from irrigation runoff, crop dusting, 5ewage, and industry. One collection indicated water temperatures as high as 82 degrees. Found in small groups over widely scattered areas, occurring at ·depths of. 18- 24 inches in rather fast-flowing water over fine sand. Life History Length of time required for development unknown. Adults have been reared in 'August. Taxonomy Day, 1955. Pan-Pacific Ent. 31(8): 127. Type species: A. inde- prensus Day; type locality: Tuolumne River, Stanislaus County, Calif6rnia. 8 BULLETIN FLORIDA STATE MUSEUM Vol. 4 ARTHROPLEA BENGTSSON United States Canada Specie5 S.E. N.E. C. S.W. N.W. E. C. W. bipunctata MeDunnough OXOOO XOO Characteristics Head strongly depressed; eyes dorsal; maxillary palp unique in of Nymphs its extreme length, being more than 6 times as long as galea- lacinia, curved and provided with long movable setae arranged in 2 rows, forming basket-like appararus. Normally, makillar.y palps held extended posteriorly over the thoracic nbtum. Tar- sal claws short and stout at base. Pair of single gills present on each of first 7 abdominal segments; each gill piatelike and pointed at apex. Three caudal filaments. Body length: 7.5-9.5 mm. Illustration: Burks, 1958, Rg. 895. Habitat of Nymphs recorded in vegetation along edge of millpond and in Nymphs a deep, rock pool at edge of a stream, where they were seen cfawling·on vegetation; appears well adapted to living in quiet waters. Taxonomy Bengtsson, 1908. kungliga Svenska Vetenskapsakademien Ars- bok 6: 239. Type species: A. congener Bengtsson; type locality: Vdrmland, Sweden. BAETISCA WALSH X O O O O X X X O O - United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. baikoui Neave O 0 O 0 callofa Traver OX 00 carolina Traver XO 00 escambiensis Berner X 0 06 gibbera Berner X 0 00 lacustris Clemens 0 0 00 % 0 0 0 0 % 0 0 0 0 0 0 0 0 0 0 0 0 0 0 laurentind McDunnough 00 00 0 X X O O X X O O K obesa (Say) X -X X O rogersi Berner .XO O, O rubesce,is Provancher O 0 00 Characteristics Stout bodied. Unique among American genera in possessing of Nymphs large mesonotal shield, or carapace, completely covering dorsum of meso- and metathorax and abdominal segments 1-5 as well as basal half of 6; apical margin fits into pyramidal elevation on tergite 6; shield often with prominent lateral spines. Gilts present on segments 2-6 and enclosed in gill chamber -covered by shield. Head frequently bears prominent frontal projections and spinous projections from the anterior angle of the genae. Legs short; tarsal claws rather long· and slender, curved, sharp at 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 9 the tip, not denticulate. Postero-lateral spines usually well de- veloped on abdominal segments 6-9. Three caudal Elaments; short, , approximately equal in length. Body length: 4-18 mm. Illustration. Berner, 1950, pl. XI. Habitat of In small to moderate-sized streams and along the edges of Nymphs lakes where there .is some wave action. Nymphs live partially buried in sand.in lee of rocks or gravel or in pebbly riffles where they are somewhat protected. One species in quiet waters near or at banks of slow-flowing streams. Other species partially buried on sandbars whefe thefe is a slight mixture of silt and sand. Chiefly herbivorous. Habits of When quiet, often h6ld caudal filaments over abdomen. Swim Nymphs by pulling legs under body, drawing together and depressing tails and. rapidly vibrating the posterior portion of body. Swim in short spurts. When nymphs come to rest, spread legs -and seize some supporting object. When at rest on sand, often have their body partially covered and become so well concealed that they are dimcult to detect against background. Life History Probably require one year to complete development. When ready to emerge nymphs crawl out of water onto any object protruding above surface. Emerge at almost any time of day, but most often in morning. Subimagal life lasts from 18-52 hours. Taxonomy Walsh, 1862. Proc. Acad. Nat. Sci. Philad. p. 378. Type spe- cies: B. obesa (Say); type localityj Rock Island, Illinois. BAETIS LEACH . United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. adonis Traver .00OXO O 0 akataleptos MeDunnough 00000 0 X alius Day O00XO 0 0 amplus Traver X 0 00 0 0 anachris Burks 0 0 0 O 0 austratis Traver 0 0 0 0 baeticatus Burks 0 0 0 0 bicaudatus Dodds o x o O 0 '0 0 > : 0 > 1 0 0 0 0 > 1 0 O ·-* ·0 -·.* 0 . 0 0 x -o _ 0 0 0 0 0 0 0 0 > < 0 > 4 0 > 1 0 0 brunneitolor McDunnough 00 0 caurinus Edmunds and Allen - .0 x cingulatus McDunnough 00 cleptis Burks 00 0 0 * 0 * 0 0 culiosus (MeDunnough) 00 devinctus ·Traver - - - 0 ·-x o 0 0 , 0 0 0 0 0 0 0 0 C o '0 0 0diablus.Day o x o 10 BULLETIN FLORIDA STATE MUSEUM Vol. 4 United States Canada Species S.E. N.E. C. S.W. N.W. E. W. elachistus Burks o x 0 0 0 endymion Traver O X O 0 0 ephippiatus Traver O 0 0 0 0 erebus Traver OX O 0 8auistriga MeDunnough 0 0 X 0 foemina MeDunnough O 0 X O frit>olus MeDunnough o x o frondalis MeDunnough o x o 0 0 X X 0 0 0 '0 0 0 0 0 0 > : 0 0 0 0 0 0 0 0 > 4 0 0 0 0 0 > < 0 0 2 . 0 > 1 0 0 0 >< 0 0 0 0 0 0 0 0 0 0 0 -0 0 0 % 0 0 0 0 0 0 0 0 0 0 0 0 * 0 0 0 0 0 0 0 0 0 0 © X 0 0 0 0 0 0 0 0 0 0 0 0 0 > 1 0 0 0 0 . O O O O O O O O O O O X o c o o ham MeDunnou*h 0 0 0 herodes Burks 0 0 0 hien%alis Leonard 0 0 0 hudsonicus Ide 0 0 0 0 insidn#icans McDunnough o x x intercataris MeDunnough x 0 0 intermedius Dodds o x o iesmondensis McDunnough O 0 0 X lapponica (Bengtsson) 06 0 00 Lgechi Day · O 0 0 0 0 levitans MeDunnough XX 00 00 macdunnought Ide 0 0 0 mollati Dodds 0 0 0 nanus MeDunnough 0 6 6 ochris Burks · ,0 0 palisadi Mayo o > < > E x K R O O > < 0 0 0 0 0 0 0 0 > t o x o O O C K O O O , K > < O O K o o c o W O K O O > < O X X C O 0 0 0 > < O O O K > < M O C pallidulus MeDunnough o paraltelus Banks o pan>US Dodcls o persecuta MeDunnough o O K O O K . O K > < O X C O O O X O X O O L O O K O X X O C O O O K 0 0 0 0 X X 0 0 0 0 . 0 phoebus MeDunnough o phyllis Burks 0 0 piscatoris Traver x o pluto MeDunnough 0 0 posticatus (Say) X, 0 propinquus (Walsh) 0 X O pygmaeus (Hagen) x O 0 quitleri MeDunnough 0 0 0 rusticans MeDunnough x 0 0 spinosus MeDunnough x X O st?iethi Berner 0 0 0 sulfurosus Day 0 0 0 thermophilos MeDunnough 0 0 0 tricaudatus Dodds 00 O 0 unicolor (Hagen) OXO , 00 vag,ms McDunnough 0XX O 0 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 11 Characteristics Body sIender, stredmlined. Head rounded, eyes lateral; a nar- of Nymphs row but distinct median notch on the apical margin of labrum; distal joint of labial palp rounded; tarsal claws with numerous fine denticles on inner margins. Ggls present on segments 1-7, single on all segments; in most species gills obovate, but in some those 6f segments 6 and 7 may be narrow and lanceolate. In most species, 3 caudal filaments;.in a few only 2 with a vestige 6f median. In species with 8 tails, the middle shorter and weaker than laterals. Body length: 3-7 mm. Illustration: Ber- ner, 1950, pl. XXII. Habitat of Usually live in shallow, flowing water. Most commonly found Nymphs under stones and rocks, among debris, 6r in vegetation along banks of creeks or rivers. Depending on species, nymphs are capable of living in water ranging from relatively quiet and slow-flowing to that whith is virtually torrential. A few species live at lake shores whe~e there is continuous wave action. Some species are highly tolerant to high temperatures, especially in southeast; others severely restricted, to colder mountain or, northern streams. Habits of Swim easily and readily. When nymphs stop, seize some area Nymphs of attachment with their claws, raise abdomen well above sup- ' port. Gills held close to and over abdomen in some species; in others, gills held out from abdomen. When stimulated to move, nymphs' dart in short spurts from one spot to another by rapidly fiipping caudal filaments up and down. In those species with 3 caudal filaments, hairs on maments overlap to form effective organ for rapid swimming. Cling closely to resting places, heading upstream, abdomen swinging from side to side in cur- rent. Nymphs crawl slowly over surface· of leaves or rocks hearching for bits of food. Positive rheotropic orientation main- tained regardless of whAher nymph is on upper or underside of support. Feeding appears to be entirely herbivorous. Life History In Florida, adults of Baetis emerge throughout year. Far- ther north season much more restricted with principal emergence - occurring during summer months. Time required for nymphs to mature in various parts of North America varies with area. Undoubtedly, in warmer portions may be more than 2 genera- tions per year; in warmer streams of colder, more northern por- tions of range, may be as many as 2 generations in the same season.. Females have been observed ovipositing by alighting on a partially submerged stone, wrapping wings around the abdomen, and crawling into the water. Once below water sur- face, eggs are glued over the stone. Eggs hatch in laboratory in 28 days. Life history in more northern portion of range may take from 6 to 9 months. One species has been shown to pass through 27 instars. Emergence occurs during daylight hours; time of emergeilce varies with species and with season. 12 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Subimagal life may last from 7 to 12 hours. When ready for emergence, nymph floats at surface Of water and dlmost immedi- ately subimago bursts free; whole process takes 5-10 seconds. Taxonomy Leach, 1815. Brewst. Edinb. Encycl. 9: 187. Type species: B. bioculatus (Linnaeus); type locality: Europe. BAETODES NEEDHAM AND MURPHY United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. species ? OOXOOOOO Characteristics Body streamlined. Head rounded; eyes lateral. Tarsal claws 6f Nymphs short and stout, bearing a series of coarse teeth. Ventrally- i directed gilts present on segments 1-5 only; usually with a row of median, raised projections on the middle abdominal tergites. Two caudal fllaments; median filament reduced to stub; lateral tails bare of hairs, or, at most, with only a few inconspicuous setae. Body length: 7-8 mm. Illustration: Traver, 1944, Ag. 11. Habitat of In very swift rapids in moderate-sized streams where they cling Nymphs to rocks and vegetation. Life History Unknown. No adults recorded from North America, Taxonomy ~ Needham and Murphy, 1924. Bull. Lloyd Library. 24 (Ent. ser. 4): 55. Type species: B. serratus Needham and Murphy; type locality: Tijuca, Rio de Janeiro, Brazil. BRACHYCERCUS CURTIS United States , Canada Species S.E. N.E. C. S.W. N.W. C. W. flauus Traver OOXOO O 0 lacustris (Needham) OXXOO O 0 maculatus Berner XOO0O O 0 W 0 % 0 0 0 0 nitidus (Traver) XOO O 0 O 0 prudens (McDunnough) 00XOO X 0 species ? Oooxo O 0 Characteristics Body flattened, broad. Head rounded; eyes lateral; head with of Nymphs 8 tubercles. No hind wing pads present. Fore. legs relatively short; middle and hind legs longer; claws long and slender. Dorsal surface of the abdoli\en depressed; lateral margins of abdominal segments produced as broad, flat, bladelike projec- tions. A pair of single, filamentous gills on 1st abdominal seg- ment; gills on segment 2 operculate and semiquadrate; gills on segments 8-6 single; margins of each gill with a fringe of long 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 18 Elaments. Operculate gills mostly covering the gills posterior to them. Three caudal filaments. Body length: 8-8 mm. Illus- tration: Berner, 1950, pl. XVIII. Habitat 6f In flowing streams where, they live close to edge on sand with a Nymphs very thin 6verburden of silt. Most frequently occur where water is 8 or 4 inches deep; however, they have been taken from water as deep as 20 feet in sandy rivers where they apparently live partially buried in silt accumulated behind sandy ridges formed on stream bed. Nymphs have also been taken from shores of lakes. . Habits of . When taken from water scarely move, probably because of Nymphs their long, spindly legs and attenuated claws. Nymphs flick tails over the abdomen when they walk. In the natural habitat are partially covered by silt. Life History Time required for nymphal development has not been deter- mined. There is some likelihood that in the extreme southeast adults emerge throughout the year; farther north emergence restricted to warmer months of summer. Emergence in Canada has been recorded as late as early September. Emergence of subimago probably occurs after dark. The time required for subimaginal molt is unknown, but adult life is very brief, lasting only afew hours. Taxonomy Curtis, 1834. London Edin. Philos. Mag. s. 8,4: 122. Type species: B. harrisella Curtis; type locality: England. CAENIS STEPHENS' United States Canada Species, S.E. N.E. S.W.. N.W. E. C. W. amica Hagen 0 0 0 anceps Traver '0 0 0 delicata Traver ' 0 0 0 O O O 'K X O C K K X X X O 0 0 0 . 0 0 0 0 diminuta Walker ' 0 0 0 foreipata MeDunnough O 0 X 0 X X 0 0 > 1 0 · 0 ·>1 gigas Burks 00 0 6 6 x >1 0 >¢ >4 M > 1 0 0 k X O hilaris (Say) ' 0 0 ' facosa McDunnough 0 0 0 0 x C X X X >~ 0 >1 0 0 .> 1 X latipennis Banks 0 X 0 punctata MeDunnough 0 0 0 0 0 0 ;< 0 0 X X ridens McDunnough 0 0 0 0 simulans MeDunnough. o x x x tardata,Megunnough o o ,0 Characteristics Body somewhat flattened, chunky. Head rounded; eyes latpral; of Nymphs apical maigih of labrum slightly concave. No hind wing pads present. Fore legs somewhat shorter than the middle and hibd 14 BULLETIN FLORIDA STATE MUSEUM Vol. 4 legs; tarsal claws slender, somewhat curved apically. First ab- dominal segment with a pair of prominent, single, filamentous gills. Gills on 2nd segment single, quadrate and operculate. Gills on segments 3-6 single and platelike, each gill having mar- gins deeply fissured to produce marginal fringe of long filaments; each Element is secondarily divided along tip to produce 2 or 8 smaller filaments. Postero-lateral spines on middle abdominal segments present, not upourved. Three caudal filaments; a whorl of setae at each joint. Body length: 2-7 mm. Illustra- tion: Berner, 1950, pl. XVII. Habitat of Usually inhabitants of quiet or stagnant water, although some Nymphs species develop in streams. A common pond form; nymphs develop on pond bottom in the zone of rooted vegetation. May also b6 found among accumulations of leaf debris and trash. In 5treams can be found at banks where they dwell close to bases of plants in silt which accumulates there. Some species occur among exposed, well-washed roots of terrestial plants along the margins of streams, but even here they are very close to substrate. Species that dwell in streams can sometimes be found in riffles or on sticks, leaves, or other debris that may be anchored in flowing water. Nymphs of some species rather tolerant of considerable amounts of pollution. Even very small bodies of fresh water serve as habitats of Caenis; nymphs having been found in puddles left behind by recession of flooded streams. Sometimes found at edges of lakes which are overgrown with vegetation. Probably the most tolerant of North · American hymphs to ~ stagnant water conditions: Habits of Omnivorous, feeding chiefly on plant material, but sometimes Nymphs feeding on dead nymphs or on other organic material that may come their way. When taken from water, nymphs crawl slowly with a wriggling moti6n. Life History In Florida, C. diminuta.has been reared in a ppriod of 4 months. Time required for hatching eggs of C. dimin'uta varied from 5 days to 11 days. Apparently, the difference in time required dependent on time of year in which eggs were laid. Some indi- cation that eggs of fall and winter broods hatch much more rapidly than those of spring. Number of nymphal instars not determined. Emergence occurs in afternoon 6r at night. When ready to transform nymphs float at the surface in shallow water. Subimago bursts free from the nymphal skin and then takes flight. Resting on some support almost immediately molts to imagal stage. M6lt occurs approximately 5 to. 6 minutes after emergence. The adults live 3 to 4 hours. Subimagoes and adults are strongly positively phototropic. In mor6 northern part df range, species emerge chiefly in June and July with sporadic emergences occurring in May and September. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 15 Taxonomy Stephens, 1885. Ill. Brit. Ent. 6: 61, Type species: C. macura Stephens, type locality: London, England. CALLIBAETIS EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. americanus Banks 0 0 x brevicostatus Daggy 6 0 californicus Banks- x carolus Traver coloradensis Banks K O O C O O X O X K O O O D O O K O O K O K .0 0 0 0 0 0 0 0 0 > € 0 0 0 0 0 0 0 0 0 0 doddsi Traver 0 0 0 . ) 0 0 0 0 0 % 0 0 0 0 > 1 0 > < 0 0 0 > 1 0 0 0 0 0 0 0 0 > 1 % 0 0 · X 0 0 0 0 0 · 0 0 0 0 ferrugineus (Walsh) floridanus Banks X K X X O . O O K K X X X X X X O X > t o X #uctuans (Walsh) 0 fuscus Dodds 0 0 0 hageni Eaton O 0 hebes Upholt o , 0 0 montanus Eaton 0 0 0 nigritus Banks O 0' O 0 0 pacificus Seemann o x x 0 0 0 pattidus Banks 0 0 0 0 0 0 pictus (Eaton) 0 0 0 0 pretiosus Banks x 0 0 0 0 0 semicostatus Banks 0 0 0 0 x o signatus Banks 0 0 0 0 0 0 skokianus Needham o x o x 0 0 traverae Upholt 0 0 0 6 0 0 Characteristics Body streamlined. Head rounded; eyes lateral. Tarsal claws of' Nymphs long and slender, provided with a row of minute, ventral den- ticles. Seven pairs of abdominal gills; sheetlike and slightly undulated with a dense net of pinnately branched tracheae; 1st and 2nd pairs of gills double, with ventral member often bear- ing secondary recurved, ventral flap; gill 7 either with or with- out recurved.flap. Three caudal filaments about equal in length and thickness; median filament fringed. on both sides with long setae; lateral Elaments fringed on medial side only. Body length: 6-10 mm. Illustration: Berner, 1950, pl: XIX. Habitat of In still water such as permanent ponds, roadside ditches, margins Nymphs of lakes, or in transient pools in which water has remained for several weeks where nymphs climb amid veg6tation, Show very wide limits of toleration. In some places where they occur in great abundance, water may be choked with vegetation; in others, vegetation may be very sparse. Temperature of water in. which nymphs occur may sometimes rise to 90 degrees in 16 BULLETIN FLORIDA STATE MUSEUM Vol. 4 southern portion of Florida, while in. northern part of its range temperature may be far below this. Nymphs appear to be very tolerant of acidity and alkalinity of water and one species has been reported from brackish water. Occasionally, nymphs are found on vegetation in backwaters of streams or along the mar- gins where there is virtually no flow. Habits of Among most graceful of all mayfly immatures. With body Nymphs arched, insects hang from plant stem and blend almost perfectly with background. When disturbed, dart- rapidly away by rapid Ricks 6£ caudal filaments. When collected and placed against a white background, nymphs hop about much like small min- nows when attempts are made to lift them. Herbivorous, feed- ing on algae and diatoms. Life History Certain species require 6 weeks for development. Eggs are retained and develop within body of m6ther for a period, of 5 to 6 days. Usually 450-500 eggs in each · female. ' When ready to deposit young, female drops onto surface of water and releases all of them. Eggs hatch immediately upon being re- leased, young search for vegetation to which to bec6me attached. Number of molts has not been determined. Emergence of adults usually occurs in afternoon. Subimaginal molt takes place 7-9 hours after emergence. Females have been kept alive as long as 18 days in the laboratory. Male adults were seen mating with subimagal females on one occasion. Taxonomy Eaton, 1881. Ent. Mo. Mag. 17: 196. Type species: C. pictus (Eaton); type locality: Texa5. CAMPSURUS EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. decoloratus (Hagen) 0 0 X O 0 0 0 0 Characteristics Mandible with an external tusk projecting forward and visible of Nymphs from above head. Front of head rounded, lacking frontal proc- esl Row of spines on outer edge 6f mandibular tusks and about 8 or 9 saw-like teeth on inner edge with proximal tooth being the largest. Legs fossorial; fore tibia broadened and flattened for digging. Seven pairs of abdominal gills; 1st gill bilobed, , small, rudimentary, one lobe much smaller than the other. Re- maining 6 pairs of gills larger, normal, bilobed, and fringed with long filaments. Three caudal filaments, median about 146 times as long as laterals. Illustration: Needham and Murphy, 1924, pl. IV. Habitat Of Unknown. Probably ,develops iii larger rivers. Nymphs 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 17 Life History Unknown. Taxonomy ' Eaton, 1868. Ent. Mo. Mag. 5: 88. Type species: C. latipennis (Walker); type locality: Para, Brazil. CENTROPTILUM EAT0N United States Canada Species S.E. N.E. C.' S.W. N.W. E. C. W. album McDunnough O 0 0 X O asperatum Traver O 0 X 0 0 bellum MeDunnough 0 0 x o bifurcatum MeDunhough 0 0 0 x chlignosum.McI)unnough u o x o conturbatum McDunnough o x o x 0 > 1 0 0 0 0 0 0 0 0 0 0 0 0 % convexum Ide o x x o 0 0 0 . 0 0 0 0 0 0 0 '0 0 0 0 X X X 0 0 0 0 0 0 .X C O O K 'O >< O X C O O O 26* Traver 0 0 0 fragile MeDunnough 0 0 x hobbst Berner o infrequens MeDunnough intermediate MoDunnough O 0 0 0 · % · 0 0 0 0 0 x O 0 0 0 X . 0 0 0 0 0 . 0 0 0 0 0 '0 0 0 0 0 0 '> 1 0 0 0 0 0 > < 0 0 0 0 . 0 0· 0 oreophilum Edmunds o ozburni MeDunhough o quaesitum MeDunnough , 0 rivulare Traver , - 0 C O O K C O C O X 0 0 , X -0 0 O 0 0 0 0 0 0 0 X O 0 , 0 0 0 0 0 0 0 rufostrigatum MeDunnough 0 O '>< O X O O '> 4 0 > * X O K O O selanderoum Edmunds , 6 semirufum MeDunnough o simile MeDunnough o venosum Traver ' 0 uictoriae MeDunnough o uiridocularis Berner - 0 walshi MoDunnough o Characteristics Body streamlined. Head rounded; eyes lateral; labial palp 8 of Nymphs segmented, distal segment dilated and truncate apically. Tarsal claws long and slender, usually not denticulate. Abdominal gills platelike and usually single on all segments; in some species, , gills of. basal segments may have a recurved, dorsal flap. Three caudal filaments; median · as long as laterals, median filament with long haih on both .sides; laterals with' 16hg hairs on medial side. Body length: 4«8 mm. Illustration: Berner, 1950, pl. XXIII. Habitat of Some species live among lilypads and pond weeds in quiet por- Nymphs tions of streams; other species occur in moderately swift water on upper surfaces of stones or on vegetation. Although nymphs are tolerant of very slow flowing water, they do not inhabit 18 BULLETIN FLORIDA STATE MUSEUM Vol. 4 ponds, but may be found ~ along edges of lakes where there is wave action. One species from Florida is confined to streams which are alkaline with pH between 7.3 and 8.0. Habits of ;When live nymphs are placed in water, tails are depressed Npnphs slightly at tips. Swim easily by rapidly flicking abdomen and holding tails stiffly out from body. Nymphs are very active. When taken out of water, hop about, flipping abdomen like a small minnow. Food is made up of plant material, Life History Length of nymphal life not determined, but. probably requires 6 to.9 months. Emergence takes place generally in late after- noon. Subimagal nidlt Within 10 to 12 hours after emergence. Some evidence indicates that time interval of later instars is between 8 and 5 days. Taxonomy Eaton, 1869. Ent. Mo. Mag. 6: 182. Type species C. luteolum (Muller); type locality: Europe. ' CHOROTERPES EATON United States Canada Species S.E. N.E. C. S.W.. N.W. W. atbiannulata MeDunnough O 0 X basalis (Banks) X O 0 ferruginea Traver 00 0 0 X X X C O O O fused Spieth O 0 6 0 0 0 , 0 0 0 0 0 0 · ~ O X O K O O O C O O 0 0 0 0 0 0 '0 0 0 huBbeth Berner O. O 0 0 0 0 0 % 0 0 0 0 inornata Eaton OX O nmlita Traver X O 0 oklahoma Traver X O 0 terratoma Seemann 0 0 X O Characteristics Body somewhat depressed. Head depress~d; eyes dorsal; labrum of Nymphs widened and deeply emarginate. Tarsal claws with row of minute blunt denticles. Gills on segment 1 single. and un- branched, linear-lanceolate; remaining gilts double, lamelli- form, each lamella having a spatulate terminal extension. Three caudal filaments; mbdian filament longer ,than laterals; hairs , present on both sides of Blaments, but relatively short and in- conspicuous. Body length: 5-8 mm. Illustration: Berner, 1950, pl. X. Habitat of In crevices on underside of rocks, logs,· or sticks anchored in Nymphs streams; may also be found in more slowly-flowing portions of streams where they live among accumulations of leaves inter- mixed with silt. Nymph5 also known from margins of lakes where there is some wave action; here nymphs also occupy crevices on underside of firmly anchored objects. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 19 Habits of ' Negatively phototropic and strongly thigmotactic. Gills held Nymphs above and close to :abdomen, where they 'are frequently vibrated. The nymphs appear to be herbivorous. Life Histofy TimB required for, nymphal development unknown; may take from 6 months to 1 year, depending on part of country in which species occurs. Transformation from nymphal to adult stage occurs after dark. Nymph, when ready to emerge, swims vig- orously to surface, subimago bursts free, floats for a moment on 6*uviae,.then flies to nearby support. Subiniaginal life lasts from 8-10 hours. In Florida emergence occurs, throughout year, reaching peak during spring and early summer. Farther north, emergence 6ccurs from July to early September. C. oklahoma adults were collected on March 20. Taxonomy Eaton, 1881. Ent. Mo. Mag. 17: 194. Type species: C. picteti , Eaton; Type 16cality: Geneva, Switzerland. 0 X X O CINYGMA EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. dimicki McDunnough 0000XOO integrum Eaton 0000XOO 4/riformis MeDunnough 0000000 species ? 00 OXO 0 0 Characteri5tics Body flattened. Head flattened; eyes dorsal. Femora flattened; of Nympbs tarsal claws relatively. short and stout at base, each claw with 2 or 3 teeth near tip. Seven pairs of gills, each gill composed of broad, platelike, dorsal element and sniall ventral tuft df fila- ments; gills do not extend over abdominal sternites; 1st gill decidedly smaller than other 6 pairs. Three tails of approxi- mately equal length. Body length: 12 mm. Illustrati6n: not illustrated in full; parts in MoDunnough, 1933,.pl. 2. Habitat of In Sierra Nevada Mfuntains occur at altitude of 8,0Od to 7,000 Nymphs feet in moderately fast water; nearly always clinging to wood and bark of dark color. Life History Unknown. Adults have been recorded from early May to late. July. Taxonomy Eaton, 1885. Trans. Linn. Soc. London: 2nd .Ser. 8: 247. Type species: C. integrum Eaton; type locality:. Washington Territory and Mount H66d, Oreg6n. 20 BULLETIN FLORIDA STATE MUSEUM Vol. 4 CINYGMULA McDUNNOUGH United States ' Canada Species S.E. N.E. C. S.W. N.W. E. C. W. confusa MeDunnough 0 0 0 x Bartrelli MeDunnough 0 0 x footenat MODunnozigh 0 0 x mimus (Eaton) 0 0 X 1)61· (Eaton) 6 x 0 0 0 * 0 0 0 0 0 0 c e o , 0 0 0 0 % 0 0 0 0 X X K K O C A W K C O O K O O X O X 0 0 0 0 0 0 0 0 0 ramalet/i (Dodds) O X reticulata MeDunnough 0 0 subaequalis (Banks) X O 0 0 0 0 0 0 0 tarda MeDunnough o x tioga Mayo · 0 0 0 0 uniformis McDunnough 0 0 0 0 x Characteristics Body depressed. Head flattened; eyes dorsal. Femora sdme- 6f Nymphs what depressed; tarsal claws short, stout, and with 3 to 5 minute, ventral teeth. Pair of gills on each of first 7 abdominal seg- ment5; gills similar on all segments, each being platelike with fibrillar portion reduced to 2 or 8 filaments; gills do not extend beneath venter. Three caudal filaments; median slightly longer , than laterals. , Body length: 7-11 mm. Illustration: not illus- trated in full; parts in MeDunnough, 1983, pl. 3. Habitat of · Often one of commonest nymphs; live under .stones in all parts. Nymplrs of stream. - In Colbrado, have· been found in some of higher streams and lakes (8,000-11,000 feet) which have clean, rocky bottoms. Wide distribution in both streams and lakes may be due to constant conditions existing under stones in both streams and lakes. Little or no current beneath rocks, and oxygen con- tefit about the same in the two environments. In streams of California, nymphs have been found in water only 1 or 2 inches deep at foot of water falls; live in crevices, and on lower surfaces of small stones in streams 6f redwood belt 6f Coast Range and Sierfa Nevadas. Life History Unknown. Adults have been taken as early as April in Southeast and as late as mid-August.in Northwest and in Canada. Taxonomy MoDunnough, 1983. Can. Ent. 65: 75. Type species: C. ramalevi (Dodds); type locality: Tolland, Cblorado. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 21 CLOEON LEACH , United States Canada Species S.E. N'.E. C. S.W. N.W. E. C. W. implicatum MeDunnough 00000 0 inanum McDunnough 0 0 0 0 0 0 ingens McDunnough , oxoxo g insignificans McDunnough 00 O 0 0 mendax Walsh O X O 0 0 0 0 5 4 .X X X > : minor McDunnough O- 0 00 0 mbropictum McDunnough XX O 0 0 0 % O X , 0 0 0 X > ~ % 0 0 0 0 0 0simplex McDunnough 00 O 0 X 0 triangulifer MeDunnough 00 O 0 X 0 vicinum Hagen o x 00 000 Characteristics Body strdamlined. Head rounded; eyes lateral; labial palp three of Nymphs segmented; apical segment Somewhat conical, the outer margin extending out farther than the inner one. Tarsal claws with very slender tips, somewhat widened at the base; finely denticu- late on the inner margin. No hind wing pad present. Seven pairs of gills; sheetlike, undulated, and usually double; tracheae usually brandhed palmately. In some species gills may be double only on 1st segment, and in others may be single on all abdom- inal segments. Three caudal flanients, approximately equal in length and thickness; hairs present on both sides of median Ela- ment and on medial side of laterals. Body length: 4-9 mm. Illustration: Eaton, 1883-88, pl. 47. Habitat of In slow-Rowing streams, or in backwaters or *liet areas along Nymphs the margins of more rapidly-flowing ones. Live among vegeta- tion, sometimes occurring. in large, numbers. Have also been taken at edge of some larger lakes and, in northern part of range, have been found in weedy areas at edge of Donds. Habits 6f Climb about on vegetation. They are apparently herbivo- Nymphs · rolls. Life History In Florida no definite seasonal period for emergence; however, farther north, in colder water, emergence restricted to warmer months. When ready to emerge, nymph rises to surface and almost immediately subimago escapes from nymphal skin. Ob- servations have indicated that females are immediately seized by males upon emergence, 56 that a rather unusual situation develops in which female subimagos mate with adult maIes. Taxonomy Leach, 1815. Brewst. Eilin. Encycl. 9: 137. Type species: C. dipterum (Linnaeus); type locality: Europe. 22 BULLETIN FLORIDA STATE MUSEUM Vol. 4 DOLANIA EDMUNDS AND TRAVER United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. americana Edmunds and Traver x 0 0 0 0 '00 0 Characteristics Body rounded. Head Rattened; antennae inserted ventrally; of Nymphs anterior margin with a pair of patches of spines and setae; three ocelli; labrum emarginate medially; mandibles small, with- out a mandibular tusk. Antero«lateral corners of pronotum pro- duced and crowned with spines, postero-lateral corners produced; prothoracic legs palp-like; mesothoracic legs highly modified, tibia and tarsus forming a spinous pad; metathoracic legs highly modified; kill legs without claws. Abdominal tergites with dense, laterally extended setae and a row of setae on the posterior mar- gin of each segment; sternites with setae. Gills on segments 1-7, carried in Ventral position; all gills with fringed margins; first gill single, others two-branched. Three caudal filaments variable in length; median Blament as long as or nearly as long as laterals. Body length: 18 mm. Illustration: Edmunds and Traver, 1959, fgs. 1-11. Habitat of Large rivers or tributaries with sandy bottoms. Nymphs ap- Nymphs parently adapted for burrowing in sand. One nymph collected in silt in stream margin, but normal habitat probably in mod- erately clean sand in fairly swift current. Habits of When placed in water, nymphs swim downward quickly and Nymphs burrow into sand disappearing almost immediately. Forward motion in sand seems to be effected by burrowing action of forelegs and elongated labial and maxillary palpi. Head seems to act much like bulldozer blade, and in part to protect mouth- parts and eyes. Thoracic prolongations and drawn-up, chelipod- like middle legs box-in ventraI, anterior, bulky half of animal thus increasing its efficiency as a burrowe~· Trailing hind tibia and tarsi lie just below ventral rows pf gills, maintaining space free of sand at all times. Life History Unknown. Taxonomy Edinunds and Traver, 1959. Ent. Soc. Amer., Ann. 52(1): 46. Type species: D. americana Edmunds and Traver; type locality: 25 miles south of Aiken, Upp6r Three Runs, South Carolina. EDMUNDSIUS DAY United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. agms Day oooxo 000 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 28 Characteri5tics Streamlined body.form. Head rounded; eyes lateral; frontal of Nymphs margin of labrum broadly and deeply excavated. Meso- and metathorkcic thrsal claws almost twice the length of the protho- racic tarsal claws. Postero-lateral angles of the apical abdomi- nal segments prolonged into thin, flat, lateral spines; gills double on 1st and 2nd abdominal segments with ventral lamella about 2/3 as large as dorsal lamella, other gms large, regularly oval, single. Three caudal filaments of equal length. Middle tail heavily fringed with long hairs on both sidds; lateral Rlaments heavily fringed on inner side. Body length: 15 to 17 mm. Illus- tration: not illustrated in full; parts in Day, 1956, figs. 8: 27, m, q. Habitat of Live in quiet, shallow, well-aerated streams. Rest close to Nymphs shady edges of pools on sand or fine gravel bottoms. Found in streams at elevations of 5,060-8,000 feet. Life History Emerge between sunset and sunrise. Maturity reached during July and early August. Duration of nymphal life unknown. Taxonomy Day, 1958. Paft-Pacif. Ent. 29(1): 19. Type species: E. agms Day; type locality: Willow Creek, Madera County, California. EPHEMERA LINNAEUS United States Canada Species S.E.. N,E. C. S.W. N.W. E. W. blanda Traver XO00 00 compar Hagen 000X 00 guttulata Pictet X X 0 0 X 0 0 0 · 0 > < 0 O 0 0 0 % 0 0 0 simulans Walker x x x x x x traterae Spieth 00XO 00 triplex Traver 0*00000 uaria Eaton XX XOOXO Characteristics Mandibles with external tusks projecting forward and yisible of Nymphs fr6m above. Frontal pr6cess on head bifid, mandibular tusks slender, upcurved apically in lateral view, margins smaoth. Legs fossorial; foreleg fiattened and broadened for digging; legs moderately stout and somewhat Battened and twisted, clothed with long, yellowish hairs on all exposed sides; fore tibia moderately flattened, widened from tbe base outward only to midway its length; tarsus more than twice as long as wide, and more than half as long as tibia. Abdominal gills present on segments 1-7; gilts narrow, margined on each side by a fringe of hairs at least twice as long as the width of gill. Body length: 12-20 mm. Illustration: Eaton, 1883-88, pl. 80. 24 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Habitat of In streams and lakes, where they burrow in sand with a small Nymphs admixture of silt. In streams nymphs tend to be in the quieter areas where current reduced. Streams where nymphs occur vary from very ,small creeks to very large rivers, depending on the species. E. simulans very common in Lake Winnepeg, Can- ada, where· nymphs live in shallow, sandy bays. In lakes, nymphs live in water not more than a few meters deep. Habits of When taken from their burrows and placed on sand, nymphs Nymphs . immediately begin burrowing. Show a· very pronounced nega- tive phototropism. When kept in water free of sand, gills are moved in undulating fashion, movement beginning at the an- terior end of body and moving progressively posteriorly. Nymphs are poor swimmers, progression being accomplished by undulat- ing movements of entire abdomen. Life Hist6ry Life history of E. simulans only has been determined. At Lake Wawasee, Indiana, main emergence occurred during last of May and first few days of June. Eggs hatched within 14 days in the laboratory. Estimated that under natural conditions from 20 to 80 days required for deyelopment. On hatching young nymphs are negatively phototropic, positively thigmotropic, aad begin burrowing immediately. Growth of specimens during summer months is rapid, nymphs increasing approximately 7 mm. in 89 days. The growth, however, is variable. This rate of development does not continue through winter but is a function of temperature. Assumed that growth slows as water codls, but nymphs are probably almost of mature length before winter arrives. On basis Of evidence gathered at Lake Wa- wasee, appears that life cycle requires one year. Emergence in other areas occurs from May to August. Tax6nomy Linnaeus, 1758. Syst. Nat. ed. 10: 546. Type species: E. vulgata Linnaeus; type locality: Europe. EPHEMERELLA WALSH United States Canada Species S.E. N.E. , C. S.W. N.W. E. C. W. aestiua Meyunnough x o o ~ 0· 0 alleglieniensis Traver 0 0 0 0 0 argo Burks o * 0 0 0 attenuata MeDunnough 0 0 0 0 0 auricillii Bengtsson O 00X O X X O > < K O O K O > 1 0 '0 > < K O O X K 'O O 0 0 X X O 0 0 autumnalis MeDunnough 0 6 -0 0 0 berneri Allen and Edmunds x 0 0 0 0 bicolor Clemens x 0 0 0 0 bicoloroides MeDunnough 00000 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 25 United States Canada Spedies S.E. N.E. S.W. N.W. E. C. catawba Traver k 0 0 0 cherokee Traver x 0.0 choctawhatchee Berner 0 0 cognata Traver X 0 coloradensis Dodds 0 columbiella MeDunnough o 0 0 0 X M O O O X O O O O O .O O K O O O o O IX x > < 0 0 0 X X X X X 0 0 0 % 0 0 0 0 0 0 , O X X O K O O O O 0 0 0 0 0 0 0 0 0 · O X 0 0 0 O 0 'O X O 0 0 0 0 0 0 0 0 0 0 0 0 conestee Traver o 0 0 0 0 '>1 0 0 0 0 0 0 0 0 X 0 0 0 X X ( D O C O X > < X X O X X W O O 'O X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 , 0 0 0 0 0 0 · 0 0 0 0 · 0 0 0 0 0 0 0 0 0 0 0 0 0 C O O ·O X X O O O Q O O O ,> to 0 0 0 0 0 0 0 0 0 0 0 0 0 0 'O C X O cornuta Morgan X co#nutella Morgan - X * 0 6 0 0 0 0 X C X O C K K X , O X X X 0 0 coxalls McDunnougli x deficiens Morgan X delantala Mayo o depressa Ide x dod Needham 0 0 doris Traver 0 0 0 dorothea Needham X (- 0 0: X 0 euterpe Traver 0OOX 00 excrucians Walsh 06XO , 0 #auilinea McDunnough 0 0 0 X ox #avitincta MeDunnough O 0 0 0 0 0 fratercula MeDunnough x'o .0 0 x o frisoni MeDunnough 0-0 X 0 funeralis McDunnough XX glacialis carsona Day o o x glaciatis glacialis Traver 0 0 0 grandis Eaton 00 O > C O O C O O O C O O O K O O X O G O O K O O hecuba Eat6n heterocaudata McDunnough hirsuta Berner hysterix Traver inermis Eaton infrequens McDunnough X 0 0 O C O O O R O ' O P O · X C O X ingens MODunnough X inuana (Walker) 0 facobi MeDunnough 0 x Zapidula MeDunnough 0 0 lata Morgan. 0 0. 0 let>is Day x o lita Butks lodi Mayo X 0 Zongicornis Traver . O 0 lutulenta Clemens 0 0 maculata Traver oxb 0 margarita Needham 0XX 0 micheneri Traver OOX000 26 BULLETIN FLORIDA STATE MUSEUM Vol. 4 . United States Canada .Species S.E. N.E. C. S.W. N.W. E. C. W. minimella McDunnougli X0000XO motita MeDunnough OOOOOX mollitia Seemann o o x o 6 needhami MeDunnough o x 0 0 x ora Burks o xooo pelosa Mayo 0 0 x o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 '0 0 0 0 0 0 p,oserpina Traver 0 0 x o ' prudentalis MeDunnough 0 0 0 0 rotunda Morgan x x 0 0 septentrionalis MeDunnough x 0 0 0 serrata Morgan x 0 0 0 0 serratoides McDunnough x 0 0 0 0 sierra Mayo 0 0 X 0 0 simplex MeDunnough X XOO soquele Day 0 0 x o O X O C O O X > < X W O K O O O X X O O O · K O > ¢ O O , O 0 0 > < X K X X 0 > < 0 % 0 * > < 0 0 0 > 1 0 > t > < 0 0 0 0 '0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 'O X 0 0 0 0 0 0 0 sordida MeDunnough 0000 spinifera Needham OXX subcaria MeDunnough , x o o temporalis MeDunnough, XOO teresa Traver O X 0 tibialis MeDunnough o x 0 X X O X X X 0 0 > 1 0 0 trilineata Bemer 0 0 tuberculata Morgan 0 0 vernatis Banks 0 0 versimilis McDunnough 0 0 walkeri Eaton x o wai/ah Traver 0 0 * 0 0 0 0 0 0 > :wilsoni Mayo 0 0 Characteristics Very variable in body form; some slender, streamlined forms; of Nymphs others flattened ventrally with dorsum arched, and with broad, flattened feinora. Many have prominent dorsal tubercles or spines on head, thorax, legs and abdomen. Some species smooth, others densely covered with hairs. All charact6rized by having gills absent from one or more of abdominal segments 1-7. Gills may be present on segments 8-7 or 4-7, and there may be a rudimentary gill present on segment one. If present only on segments 4-7, those on 4 are operculate or semi-operculate cov· erihg all or parts of the preceding pairs of gills. In all species the gi115 wholely dorsal in position. Maxillary palp may be rudi- mentary or wanting in some species, in others may be normal. Tafsal claws of most species bear several denticles. Lateral ex- tensions usually present on the abdominal segments, bearing postero-lateral spines of greater or less development. Three caudal Blaments with spines or hair5 or both. Some of the nymphs are highly variable in color. Body length: 5-20 mm. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 27 Illustrations: Berner, 1950, pls. XIII, XIV; Day, 1956, ~gs. 3: 22. Habitat of Occur in a wide variety of habitats-in lakes where there is Nymphs wave action along shore, ift slowly ,flowing to virtually stagnant streams, and in swiftly flowing streams with rapids. Wherever they occur nymphs usually seek protection in crevices of rocks or in vegetation where flow is reduced. In some western forms, hymphs are adapted to live in torrential conditions, the abdomen beihg modified to form a sucker-disk permitting nymphs to cling to rocks in swiftest water. Fonns occurring in quiet water are very often to be found at stream banks where they bury themselves close to the bases of .plants and among roots in shallow water. Some nymphs live on top of rocks dedp within moss which may be growing on them in swift-Rowing wat6r. By scraping deeply within the moss nymphs can be found, or by taking rock from water, letting water drain away from moss, the nymphs slowly begin to climb out tofward the tops of the plants. Habits of Most nymphs cling very tightly to objects to which they are Nymphs attached when they are in water. When removed from water they remain quiescent; as they dry out some slow, deliberate movements can be seen. In aome forms nymphs Rick tails for- ward over abdomen, then straighten them out, repeating act continually. In others there is no movement at all, and it is only by careful examination that nymphs can be seen against background. Especially true 6f those nymphs taken from very swift water. Nymphs ate awkward swimmers, using undulatory movements of the abdomen for locomotion. Almost immedi- ately head for some attached object to which they can cling, arid once attached blend in perfectly with their backgrounds. Those nymphs with operculate gill covers circulate water under gills by raising one or both covers and yibrating the other pairs of gills. Nymphs are omnivorous. Life History Time required for development has not been determined, but it is likely that most species require approximately one year. In Florida emergence takes place in late winter, spring, and early summer. Some species emerge by simply floating at the surface of water, and almost immediately subimago emerges and flies away. In others, nymphs may crawl partially Out of water onto some attached object and transform. Emergence normally takes place in late afternoon, sometimes occurring after dark. Subimagal stage may take from 22 to 30 h6urs for completi6n. Taxonomy Walsh, 1862. Proc. Acad. Nat. Sci. Philad. p. 377. - Type spe- cies: E. excrucians Walsh; type locality: Rock Island, Illinois. 28 BULLETIN FLORIDA STATE MUSEUM Vol. 4 EPEORUS EATON United States Canada Species S.E. N.E. C. S.W. N.W. 'C. W. albertae (McDunnough) O 0 0 X X O arctus (Traver) O 0 0 X O californicits (Banks) O 0 X O deceptious (MeDunnough) 0 0 X o dispa~ (Traver) 000 Q dulciana (MeDunnough) 0 0 ' O 0 0 X X 0 * 0 0 0 0 0 0 0 0 % 0 0 0 flauipennis (Traver) O 0 0 fragilis (Morgan) X O 0 0 0 0 0 0 0 0 X X X 0 0 * O K > < 0 0 0 0 0 0 Ili O 0 0 0 0 0 0 X O 0 0 0 0 0 ,0 - C O O K X O > < 0 0 > 4 0 * % 0 0 0 % 0 0 0 0 0 0 0 0 0 0 0 0 frisoni (Burks) X O 0 geminatus (Eaton) O 0 0 grandis (McDunnough) 0 0 0 - ' O hesperus (Banks) O 0 0 0 lagunitas (Traver) 0 0 0 0 let)idus (Traver) O 0 0 0 x 0 0 0 > 4 x x x > < > < 0 * 0 0 0 0 longimanus (Eaton) O 0 0 0 namatus (Burks) OX O 0 nitidus (Eaton). O 0 0 permagnus (Traver) 6 pleuralis (Banks) 0 0 punctatus (MeDunnough) 0 0 rubidits (Traver) 6 0 0 >< X, 0 C O ' X subpallidus (Traver) O 0 O 0 su#usus (MeDunnough) O 0 X O vitrea (Walker) 00 X O Characteristics Body gattened and slightly convex dorsally. Head flattened; of NymDhs eyes dorsal; frontal and lateral margins of head expanded, cov- ering mouthparts completely. Legs fringed with hairs; tarsal claws short, each with 2 to 6 minute teeth near tip. Gills Dresent on segments 1-7; each gill composed of ventral plate- like element· and a much reduced tuft of filaments; anterior lobe of lamellate portion of first better developed than others. In some species anterior lobes almost, 6r c6mpletely meet beneath tha body; in other species a long space intervenes between. Posterior pair of gills may or may not project beneath abdominal venter to form, along with intermediate gills, a partial or com- plete adhesive disk. Two caudal filaments: Body length: 7-14 mm. Iliustration: Burks, 1958, fig. 886. Habitat of Live in shallow, cool Or cold, rapidly flowing water, where they Nymphs are attached to rocks, sticks, or other firmly anchored material. Habits of Because of holdfast provided by gills, nymphs hold on to rocks Nymphs tenaciously when attempts are made to remove them. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 29 Life History Length of time required f6r development unknown, but pr6bably one year. Adults have been observed emerging in aftefnoan. Nymphs rise to surface, and subimago immediately escapes from . turbulent water. Have been observed eraiwling to within an inch of surface and emerging there·from nymphal skin, breaking through surface film with wings fully expanded. Adults have been found from late May to early August. Variation in einerg- ence time probably correlated with temperature conditions under which nymph develops. Taxonomy Eaton, 1881. Ent.,Mo. Mag. 18: 26. Type species: E. torren- tium EatOn; fype locality: Taraston, Franc6. EPHORON WILLIAMSON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. album (Say) O0XXX OXO leukon Williamson X X X 0 0 X 0 0 Characteristics Mandible with an external tusk, projecting f6rward, visible from of Nymphs above head; tu5ks do*,ncufved, convergent apically; irregularly toothed on the outer margin, bearing sh6rt spines dn the dorsal and.lateral surfaces, long hairs on inner margin, a frinde of hairs of graduited length basally oh outer margin, longer apically. Head with rounded, inedian, frontal prominence. Fore legs short 'and stout, fossorial; tibae and tarsi of hind legs slander, femora moderately stout. Seven pairs of gills, all dorsal in po- sition, single on 1st segment, double on segments 2-7, each member ofa pair fringed on each 5jde with short hairs; lateral tracheae numerous, distinct. Three short caudal Blaments. Body- length: 12-16 mm. Illustration: Eatqn, 1888-88, pl: 28 (as Polymitarcys). Habitat of In swift streams in tubular burfows beneath stones partially im- Nymphs bedded in substrate. , May be under either large or small stohes, often found more comm6nly under large, flat stones. During daylight hours, nymphs g6 fairly deep in burrows; later in eye- ning, as darkness folls, come closer to surface. - Habits of Probaoly filter food that passes through burrow. Current of Nymphs * water drawn ,through burrow by movement of gills. Food is filtered out on long hairs that border fore legs. Life History Time required for development has not been determined, but estimated that full year needed for nymphal development. Adults have been taken from May to September. Adult life is extremely brief. One observation indicates that .adults live for about one hour. Emergence occurs about Aundown or shottly thereafter, with subimagil period lasting but a few minutes. 80 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Taxonomy Williamson, 1802: Trans. Amer. Soc. Phil. 5: 71. Type ,species: E. virgo (Olivier); type locality: Europe. HABROPHLEBIA EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. vibrans Needham: XXOOO 0 0 0 Characteristics Body slender and only slightly flattened. Head somewhat of Nymphs rounded; eyes lateral. Tarsal claws relatively short with a single ventral row of denticles. Seven pairs of gills, all double and narrowly lamelliform at base, but quickly breaking up into a number of linear filaments outspread at sides of abdomen. Three caudal filaments; median filamtnt longer than laterals. Body length: 4-5 mm. Illustration: Eaton, 1888-88, pl. 86. Habitat of In small streams, near the edges among v6getation or in leaf Nymphs debris where there is some accumulation of silt. Life History Not determined. Probably requires from eight to twelve months to complete development depending on the part of the country in which species occur. Adults have been collected from April to August. Taxonomy Eaton, 1881. Ent. Mo. Mag. 17: 195. Type species: H. fusca (Curtis); type locality: Europe. HABROPHLEBIODES ULMER United States Canada Species S.E. N.E. C. S.W. N.W. E. W. americana Banks XXXOOX O 0 0 0 0annu?ata Traver OOXOOO O brunneipennis Berner x 0 0 0 0 0 0 Characteristics Body slender, somewhat depressed, Head tends to be flattened; _ of Nymphs eyes lateral; anterior margin of labrum rather deeply cleft. Tar- sal claws long and slender; each bearing a single ventral row of dehticles. Seven pairs of abd6minal gills, all similar; each gill basally has a slender stem which subclivides into 2 long, slender, lanceolate filaments; a single, main, multibranched trachea. Three caudal filaments; median filament slightly longer than the laterals; all Elaments sparsely covered with short hairs. Body length: 4&6-6 mm. Illustration: Berner, 1950, pl. IX. Habitat of In slowly to moderately swift-Rowing streams where they may Nymphs occur in leaf debris. They can sometimes be found in riffles, but are most common among exposed roots of terrestial plants or in 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 81 submerged vegetation along the banks of streams. Nymphs are also found in crevices of logs which have become watersoaked and are partially rotted. ' Early instars may often be found among pebbles in riffles, but as maturity is raached, nymphs migrate into quieter water. Streams inhabited by these nymphs usually drain heavily wooded areas or bogs and are somewhat acid and tinged with brown. Habits of Gills are kept:in constant motion. When the nymphs are at rest Nymphs gills held stiffly out from the body at about 45 degree angle and slowly waved forward and backward. While swimming nymphs press gills against abdomen. Awkward swimmers; usually move most efficiently by crawling. Swim by undulatory movements, wave beginning at head and travelling to caudal filaments which are depressed or raised as unit. Caudal Glaments help very little in propelling the insect. Strongly negatively phototropic and positively rheotropic. Life History Time required for nymphal development not determined; prob- ably takes from 6 to 12 months, depending on part of country in which species lives. Emergence usually occurs in morning dr early afternoon. , When feady to transform, nyinph crawls out of water, sometimes as far as an inch above surface. After a few moments, subimago appears, rests a moment, then flies to a nearby support. SubimagaI stage lasts 12 to 14 hours. In Florida emergence occurs throughout year; farther north emerg- ence is restricted to late spring and summer months. Taxonomy Ulmer, 1919. Arch. Naturg. 85: Abt. A. 11: 39. Type species: H. americana (Ba'nks); type locality: Pasiaic, Ndw Jersey. HEPTAGENIA WALSH United States Canada Species S.E. N.E. C. S.W. N.W. E. adequata Mebunnough 0 0 0 0 aphrodite MeDunnough x 0 0 x criddlei MeDunnough 0 0 x o cruentata Walsh. o x 6 0 diabasia Burks o x 0 0 dolosa Traver x 0 0 0 0 * 0 0 0 0 0 0 > 1 0 0 0 * 0 0 0 > 1 0 0 0 * C O O C O O K 0 6 O O K O O X X O O K . 0 0 0 elegantula (Eat6n) o x 0 0 % 0 * 0 0 0 0 0 0 0 0 0 0 0 flauescens (Walsh) x x 0 0 hebe MeDunnough o x o x horrida MeDunnough 0 0 x inconspicua MeDunnough 0 0 0 julia Traver x 0 0 funo MdDunnough x o x 0 0 0 0 0 kenned!/i McDunnough 0 0 0 82 BULLETIN FLORIDA STATE MUSEUM Vol. 4 United States Canada Species, S.E..'N.E. C, S.W. N.W. E. C. W. lucidipennis (Clemens) o x x 0 0 x maculipennis (Walsh) 0 0 0 0 manifesta (Eaton) 0 0 0 0 marginalis Banks x 0 0 0 0 X ·0 0 0 0 0 0 0 0 0minerva MeDunnough x 0 0 x otiosa MeDunnough 0 0 x 0 0 0 X X X 0 0 0 0 0 0 0 0 X X O X patoka Burks 0 0 0 000 perfida MeDunnough 0 0 0 x 0 0 persimplex McDunnough 'O 0 0 0 0 putta Mci)unnough O X O X0O rodocki Traver O 0 X 000 x > < L O O K O > < K O O X O O O , O o o o fosea Traver o x 0 0 0 rusticalis MeDunnough x o x 0 0 0 0 0 * 0 X > 1 0 0 simplicioides Mebunnough o x 0 0 x solitaria McDunnough 0 0 0 0 x spinosa Traver 0 0 0 0 0 thetis Traver 0 0 0 0 0 townesi Traver 0 6 0 000 umbricata McDunnough 0 0 0 X O 0 walshi McDunnough 00 00 XOO Characteristics Body flattened. Head Rattened; eyes dorsal. Femora mod- of Nymphs erately flattened; posterior margin of each bears a dense row of hairs and a sparse_ row of short; stout spines. Gills presedt on . abdominal segments 1-7; all gills of same form, but not same size. Each gill composed of dorsal platelike element and ven- traI filamentous tuft; in some species tuft greatly reduced or lacking on 7th pair of gills. N6 gills extended beneath abdom- inal venter. Three caudal filaments, approximately of equal length. Body length: 6-12 mm. Illustration: Burks, 1953, Bg. 888 Habitat of Generally occur under stones and among debris in shallow, rap« Nymphs idly flowing water near banks of small streams and rivers. Some- times found under stones at edge of quiet pools between rapids. Also occur at margins of lakes where there is wave action and shore is rocky, or has debris to which insects may attach then* selves. Habit5 of Very active; when a stone is lifted from water, often scurry to Nymphs underside. Agile and frequently can elude attempts to lift them from surface to which they are attached; cling closely and with considerable strength. When placed in pan of water, - nymphs, provided no attaching surface available, tend to form into balls clinging to one another and tumbling about in water. 1959 BERNER: NORTH AMERICAN. MAYFLY NYMP.HS 88 Life History Eggs deposited by female as she dips abdomen into water. Hatching in the laboratory tdkes from 12 to 40 days. Length of nymphal life probably one year, although not _determined ac- curately. When ready to emerge, nymph comes close to surface and subimago bursts free. Life as adult lasts from 2 to 4 days. Adulti taken from May to October. Principal emergence in June and July. Taxonomy Walsh, 1868. Proc, Ent, Soc. Phila. 2: 197. Type species: H. #avescens (Walsh); type locality: Rock island, Illinois. HEXAGENIA WALSH United States Canada Species S.E.· N.E. C. S.W. N.W. E. C. W. atrocaudata MeDunnough x x o o x ,0 bilineata (Say) x x 0 0 6 0 limbata californica Upholt o x o 0 0 limbata linibata (Serville) x * 0 0 limbata occulta Walker o x x 0 X 0 0 > 1 0 0 0 X limbata venusta Eaton 0 0 0 limbata viridescens (Walker) o x.x O X > 0 0 < 8 0 0 * * € 0 0 > 1 X X X X W O K .~ 0 X .K 0 0 0 > < 0 . 0 0 0 0 0 0 munda a#iliata McDunnough 0 x 0 munda elegans Traver 0 0 0 munda marilandica Traver x 0 0'0 munda munda Eaton 0 0 0 0 0 0 0 0 0 0 0 6 0 0 munda orlando Traver 0 0 0 0 0 recuruata Morgan x o x 0 0 figida MeDunnough x o x .A o Characteristics Mandible with in external tusk projecting f6rward and visible of Nymphs from above head. Mandibular tusks long, slender, smooth, up- curved, tip5 divergent. Frontal process on the head entire, apical margin may be truncate, conical or rounded. Fore tibae flattened and widened, fossorial. Seven pairs of abdominal gills, narrow, tapering, and with no distinct lateral Gacheal branches; margined on' each side by fringe of hairs at least twice as long as width of' gills. Gills on 1st abdominal segment rudimentary and bifurcate; without conspicuous hairs. Three relatively short cauddl filaments. Body length: 12-82' mm. Illustration: Berner, , 1950, pl. IV. Habitat of In both streams and lakes where nymphs burrow in soft bottom. Nymphs In streams, they inhabit quieter backwaters where there· is an accumulation of silt. Burrows may occur in large number5, 6penings of which can be easily seen if water is clear. In lakes, nymphs occur in bottom muds at considerable depths. Depth in itself does not appear to have a great influence over distribution, nymphs being found from very shallow water down to 17% 34 BULLETIN FLORIDA STATE MUSEUM Vol. 4 meters; however, nymphs much scarcer in deeper waters than in more shallow aress, with maximum depth probably about 18 meters. Character of bottom of great importance in determining local distribution in lakes. Usually found in large numbers only in bottoms composed of soft mud or clay and largely restricted to a substratum which is soft, yet firm enough to permit main- tance of a burrow. Nymphs do not ordinarily inhabit sand, gravel, rubble, peat, or bottoms which are flocculent. Burrow U-shaped, both ends open to mud surface. Nymphs maintain flow of water through tunnel by rhythmitally waving gills. In- sects known to burrow to depth of 5 inches, but probably do not penetrate to depth greater than 6 inches. Appear to be unable to withstand stagnation in which dissolved oxygen con- tent of water falls below 1.0 ppm. Average numbers of H. lim- baca nymphs per square foot in Michigan lake ranged from 6 t6 80. In Lake Winnepeg estimates of 62,000,000 to 98,- 700,000 per square kilometer were given for two species. Esti- mates were made at time of maximal population density. In Michigan lakes which were studied, nymphs comprised as much as 59 percent of entire volume of macroscopic bottom fauna in suitable bottom areas. Habits of Swimming accomplished by dorso-ventral undulations of body, Nymphs chiefly of abdomen. Caudal filaments directed backward and overlap one another. Fore and middle legs directed anteriorly, hind legs posteriorly, all legs being held close to body. Gills extended up and laterally, waved continuously as swinimmg proceeds. When released.at *ater surface, nymphs usually swim vigorously downward in attempt to reach bottom quickly. Im- mediately on contact with bottom attempt to burrow. Burrow- ing accomplished in seconds. Entrance into mud gained by digging of fore legs, pushing with hind legs, and an occasional strong, undulating movement of abdominal gills. Once head and legs under mud, remainder of body quickly disappears. Size and depth of burrows depends on size 6f nymphs. Nymphs seem to be mud-eaters. Life History In Michigan, H. hmbata probably requires one year, with rate - of growth being a function of water temperature. Under lab- oratory conditions of high temperature, adults reared from egg to maturity in less than six months; in natural waters, with low temperature two years required. Number of eggs produced per female varies between 2,200 and 8,000, average female pro- ducing about 4,000. Time required for hatching variable, de- pending on ' temperature. In laboratory, hatching obtained in 11 to 26 days. Estimated that in lakes under natural conditions eggs hatch about two weeks after laying. .In northern past of range adults emerge in period of 3-6 weeks, with stragglers continuing to appear much later. Emergence occurs in late afternoon just about dusk. At time of emergence, nymph, ordi- 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 85 narily negatively phototropic and positively geotropic, reverses tropisms and swims from lake bottom or stream bottom to sur- face and breaks through surface film, adult immediately bursts free. Subimagal period lasts from 24-48 hours. In Florida H. munda orlando emerges principally during summer; strag« glers can be taken in nearly every month of year, except in midwinter. Taxonomy Walsh, 1868. Proc. Ent. Soc. Philad. 2: 197. Type species: H. bilineata (Say), type locality: North America. HOMOEONEURIA EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. ammophila Spieth 00XOO 000 dolani Edmuiids, Berner, Traver x 6 o o o 000 species ? X .0 X 0 0 000 Characteristics Body streamlined. Head rounded, eyes lateral; gills attached of Nymphs to base of maxilla. F6re femur and tibia with dense fringe of long hairs on inner side; fore tarsus reduced to small protuber- ance; other legs hairy with thin. tarsal claws. . First pair of gills ventral, and multibranched; other 6 pairs of gills dorsal,large, small, flat, and slender. Caudal filaments approximately equal in leng*; heavy fringe of hairs on both sides of median filament, lateral filaments with fringe of hairs on medial side. Body length: 9-12 mm. Illustration: Edmunds, Berner, Traver, 1958, figs. 15-29. Habitat of Found in large, moderately to rapidly Rowing streams with Nymphs shifting sand bottoms in which nymphs burrow. Habits of ' Burrow rapidly in sand and occur 1-2 inches below sand sur- Nymphs face. Awkward swimmers; when brought above level of sand, often re5t on their sides. Filter food from water with long hairs on fore legs and graze on materials so collected. Life History Length of nymphal life unknown; probably takes one year to develop from egg to adult. Emergence has not been noted. Female, with vestigial legs, probably molts on the wing, male may possibly alight to molt, as it still has some functional legs remaining. Emerge June to October. Taxonomy Eaton, 1881. Ent. Mo. Mag., p. 192. Type species: H. saluiniae Eaton; type· locality: Duefias, Guatemala. 86 BULLETIN FLORIDA STATE MUSEUM Vol. 4 ISONYCHIA EATON United States . Canada Species S.E. N.E. C. S.W. N.W. C. W. annulata Traver XO0000 arida (Say) O X 0 0 aurea Traver 0 0 0 bicolor (Walker) X O campestris MeDunnough o x X 0 X 0 X M X X X 0 8 >· 1 /1 0 O X X O 0 0 0 * ,O X O · 0 0 0 0 0 > < 0 0 0 0 christina Traver x o 0 0 0 '0 0 0 0 0 0 O 0 0 0 0 0 0 0 0 0 circe Traver 0 0 diuersa Traver 0 0 fattigi Traver 0 0 georgiae MeDunnough o harperi Traver x 0 0 intermedia Eaton O 0 0 manca Eaton 00 X 0 matilda Traver OX 00 O > < 0 0 0 0 0 O X O > < 0 0 0 0 0 > 1 0 > 5 0 'K O C O O 0 '0 X O '0 0 0 0 '0 0 0 0 0 0 '0 0 0 0 ' 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ( 0 0 0 0 0 0 0 0 * 0 0 0 0 0 0 0 0 0 0 0 ' 0 0 ¢ 0 ( 0 0 0 0 0 0 notata Traver X .0 0 obscura Traver- 0 0 pacoleta Traver 0 0 pictipes Traver 0 0 fufa McDunnough x o sadleri Traver x o sayi Burks 0 serrata Traver o sicca (Walsh) 0 similis Traver 0 0 thalia Traver X O 0 tusculanensis Berner X O 00 t>elma Needham 00 XO-O Characteristics Body streamlined. Head rounded; eyes lateral; head with a of Nymphs median frontal ridge below middle ocellus; mouthparts very hairs,. Gill tufts ptesent at the bases of maxillae. Fore tibia , with a conspicuous apical spine; fore leg with fringes of long spinelike hairs on femur, tibia, and tarsus. Gill tufts present at base of fore coxa; claws stout and denticulate on inner margin. Gms present on first 7 segments; each gill consisting of a basal filamentous portion, covered by a dorsal platelike portion. Three caudal flaments; median filament with heavy fringe of hairs on both sides; lateral filaments with hairs on the medial side. Body length: 9-17 mm. Illustration: Berner, 1950, pl. VI. Habitat of Vigorous 'swimming forms found in rapidly Rowing water of Nymphs , creeks and rivers. Nymphs occur in tangle5 of vegetation and debris anchored in stream, especially on branches and collections of leaves caught in swift Row. May be found-concentrated in large numbers where branches trail in flowihg ·water. Nymphs / 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 87 on rocks or on Rat rock ledges where there is considerable dis- turbance of the water as it pour5 across surface. Ndgatively phototropic. Habits of Very strong swimmers; face current with fore legs held in front Nymphs. of mouth, long hairs overlapping, and filtering food from figw- ing water. Fr6m time to time they graze on materials caught on hairs. Life History In warmer parts of coastal plain of southea5t, emergence may occur throughout year, in colder areas emergence limited, to warmer months. Length of time required for nymphal develop- ment not determined, but probably requires approximately one year. To emerge, nyniph leaves water by erawling a few inches above water surface onto rocks, sticks or,any other protruding 6bject. Length of time as subimago varies between 22 and 81 hours. Emergence occurs in late afternoon or shortly after dark, with an occasional subimago appearing in early ·morning. Taxonomy Eaton,·1871. Trans. Ent, Soc. London, p. 184. Type species: I. ignota (Walker); type locality: unknown, p'robably Europe. LACHLANIA HAGEN United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. powak Edmunds 000 X 0 000 saskatchewanensis Ide 00000 OXO Characteristics Body somewhat depressed. Head more or less flattened; eyes of Nymphs dorsal; maxilla with tuft of gills at base. Fore tibia and femur bearing long fringe of hairs on inner sides; short, st6ut tarsal claws. Abdomen- somewhat flattened with lateral margins pro- longed into rather coarse postero-lateral spines. First pair of gills ventral, small; remaining 6 pairs dorsal, platelike, sinall. Two caudal filaments with rather sparse fringe of hairs on inner margin. Body length: 8-10 mm. Illustration: Edmunds, 1951, fig. 8. Habitat of Mainly found clingihg to small sticks lodged in interstices of Nymphs rocks in rapids ot on uhdersides of rocks. Habits of When disturbed, nymphs tip tails· up over back: Slow moving; Nymphs cling t6 sticks and rocks with great tenacity. Life History Unknown. Mating flights have been observed as early as 7:45 a.m. Subimaginal skin shed from all parts of body except wings . while insects ate in flight. Length of adult life extremely short, perhaps not- more than 4 or 5 hours. Sw-armihg observed in Utah in early September. 38 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Taxonomy Hagen, 1868. Proc. Soc. Nat. Hist. Boston. p. 373. Type species: L. abnormis Hagen; type locality: Cuba. LEPTOHYPHES EATON United States Canada Species, ' S.E. N.E. C. S.W. N.W. E. C. W. species ? 00 X O 0,000 Characteristics Body flattened. Head rounded; eyes lateral. Short, thickset of Nymphs legs wiih edentate tarsal claw5. Hind wing- pads present. Ab- dominal gills at lateral margins of segments 2-6; 1st pair elon- gate, oval, and elytriod covering following pairs. Lateral mar- gins of abd6minal segments produced as broad, shelf-like projec- tions with. postero-lateral angles acute. Three caudal filaments. Body length: 3-5 mm. Illustration: Needham and Murphy, 1924, pl. VII, Bgs. 79-88, 91-95. Habitat of In larger rivers where they occur on sticks, logs, and branches Nymphs which have fallen into the water. Life History Unknown. Taxonomy Eaton, 1882. Ent. Mo. Mag. 18: 208. Type species: L. eximius Eaton; type locality: Cordova, Argentina. LEPTOPHLEBIA WESTWOOD United States Canada Specie's S.E. N.E. S.W. N.W. C. W. at*strina (Traver) X 0 0 0 comna (Traver) 0 0 0 0 0 0 * 0 0 0 % 4 0 0 M O O , 0 0 0 0 0 0 0 0 0 cupida (Say) x x grandis (Traver) 0 0 gracestella (Eaton) 0 0 - 0 0 X X O X > 1 > < 0 0 · 0 0 > lo O K O interme,lia (Traver) 0 0 0 0 0 % 0 0 X X johnsoni MeDunnough X 0 X O nebutosa (Walker) XX X O pacifica (McDunnough) 00 O 0 Characteristics Stout-bodied. Rounded head; eyes lateral. Thorax and abdo- of Nymphs men slightly Battened on dorsum. Tarsal claws with rows of ventral denticles. Seven pairs of abdominal gilla; double and lamelliform on all 7 segments, narrowly so on segment one. On segments 2 through 7 gills double and quite broad; each lamella has a terminal Elamentous extension. Three caudal filaments; approximately equal in length. Body length: 7-15 mm. Illustration: Berner, 1950, pl. VII (as Blastums). 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 89 Habitat of In parts of range develop in ponds Of in quiet eddies along Nymphs banks of streams. In southeast nymphs found only in flowing water or in backwaters of streams. Poorly adapted for swift water and rarely found other than in quieter portions of streams or in pools recently cut off from streams. Associated with quiet area near the banks, in pools where dead leaves may accumulate, or at submerged mossy banks where nymphs crawl amid the bases of the plants. During time of emergence, nymphs migrate 'into .quiet backwaters where. they become highly concentrated „ in. favorable situations lacking water m6vement and water is relatively shallow. Usually concentrate among layer5 of leaf debris. Large gill expanse probably correlated with low oxygen content of almost stagnant water in which nymphs live. Habits of Omnivorous, feeding on detritus,+ diatoms, algae, and cast sldns Nymphs of. nymphs of their own or other species. Nymphs negatively phototropic, seeking- dark underside of any materials that are available. When kept in the laboratory, and room is darkened, nymphs move to upper surface. of the substrate. However, when light is switched on nymphs scurry away into some dark crevice. Nymphs about to emerge undergo a phototactic re- versal. Crawl to upper side of leaves or onto sticks, logs or any other available support near surface of water. L. cupida has been shown, in Manitoba, t6 migrate up temporary streams formed by melting snow, some nymphs even leaving the water and crawling along banks in moving upstream; may migrate as much as· 300 to. 400 yards a day. Life History Time required for nymphal development unknown, but probably one year. Estimate based on concentration of mature nymphs id backwaters during one definite period. Mature nymph moves to surface and subimago emerges. Some nymphs crawl Out of the water, but, generally, emergence is at the surface. Emerg- ence may occur at any time of day with height of transformation in early aftern66n. Subimaginal stage lasts from 18 to 29 hours. In Florida, emergence was reported as early as late January with the peak of emergence in February to early March. Farther north emergence occurs as early as February, then con- tinues on int6 May. In southern Canada species emerge in late May and continue emergence into late June. Taxonomy Westwooa, 1840, Introd. Mod. Classif. Ins. 2.81. Type spe- cies: L. vespertina (Linnaeus); type locality: Europe. 40 BULLETIN FLORIDA STATE' MUSEUM Vol. 4 , METRETOPUS EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. borealis Eaton 00000 XXX Characteristics Body streamlined. Head rounded; eyes lateral. Terminal seg- of Nymphs ment of labial palp expanded and truncate apically. Legs fairly 16ng; tarsi longer than tibae; femora almost as long as the tibae and tarsi together. Tarsal claws of prothoracic leg differ from ' those of the other legs in being bifid. Gills on segments 1-7 similar in form and single. Three tails; middle one fringed with long hairs on both sides, the lateral caudal filaments fringed on medial side only. Not illustrated. Habitat of Nymphs probably occur in slow-Rowing streams on vegetation Nymphs or on the bottom near the shore. Life History Adults have been taken in late July and mid-August in Canada. Taxonomy Eaton, 1901. Ent. Mo. Mag. 2nd. ser. 12.258. Type specie5: M. noreegicus Eaton; type locality: Aal, Norway. NEOCLOEON TRAVER United States Canada Species - S.E. N.E. C. S.W. N.W. E. C. W. alamance Traver X O X O 0 000 ~ Characteristics Body streamlined. Head. rounded; eyes lateral; labial palp three of Nymphs segmented, distal segment widely dilated apically, especially on , inner margin. Tarsal claw5 very long and slender, not denticu- late, almost % as long as their respective tarsi. Seven pairs of abdominal gills, single on all segments; middle gills irregularly rounded, others more or less straight on outer margins; tracheae pinnate, . Three caudal filaments of approximately equal length; median filament with long hairs OIl both sides; laterals with hairs on medial side. Body lehgth: 5-6 ·mm. Illustration: - Needham, Traver and Hsu, 1985, pl. XL. Habitat of Collected from small, spring-fed streams; probably occur among Nymphs vegetation in more slowly-flowing poktion of stream. Nymphs were also found in masses of plants in slow-flowing current of spring-fed tributaties. Life History Length of nymphal life unknown; probably requires six to nine months for development. Earliest recorded emergence Febru- ary 7; the latest mid-April. Emergence occurs in the morning. Subimaginal period apparently lasts 6 to 7 hours. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 41 Taxonomy Traver, 1982. Jour. N.. Y. Ent. Soc. 40: 365. Type species: N. alamance Traver, type locality: Big Alamance Creek, North Carolina. NEOEPHEMERA McDUNNOUGH United States Canada Species S.E. N.E. C. S.W. N.W. C. bicolor McDunnough OOX00 0 X C O O compressa Berner X 0 0 0 0 0 0 0 0 0purpurea (Traver) x 0 0 0 0 0 youngi Berner X0000 0 Characteristics Body elongate. Head rounded; eyes lateral; head almost twice of Nymphs as wide as long. Prothorax. longer at margins than at midline. Legs long and spiderlike; tarsal claws simple, curved. First abdominal segment ~with a pair of vestigial filamentous gills; gills on segment 2 fused to form. elytroid plates covering following 4 pairs. Prominent median spine on tergites 1 and 2, Lateral margins of segments 8-9 prolonged posteriorly into flattened processes that may be decurved; exceptionally well developed on segments 6-9. Three caudal Rlaments with rings of stiff hairs at joints. Body length: 8-17 mm. Illustration: Berner, 1956, Bgs. 1-14. Habitat of In streams of slow to moderately swift flow. ,Nymphs of.most Nymphs species occur in debris which is anchored in flowing water. May aldo occur in large numbers among exposed, well-washed roots of terrestial plants; frequently found among tangles of branches washed into. stream. Some species have been takenliving deep within moss which is also exposed to current. N. purpurea sometimes occurs under large, flat rocks in midstream where flow of water is swift; however, nymphs occur in protected places, well away from the current. Habits 6f Slowly moving insects. When dislodged, swim with great diffi- Nymphs culty with legs .outspmad; almost immediately settle to bottom and become attached to some object to which they cling tenaci- ously. They swim but little, and their motions are extremely ' awkward when they do. Tails are bent over abdomen and sud- denly lashed 56 that movement of abdomen, assisted by the beating of almost bare caudal filaments, propels, the insect. Attitude of nymphs when taken from water is characterized by a slow, deliberate movement with occasional flicking motion of the caudal filaments as insect brings them completely back over its dorsum until they point, anteriorly, then lashes out with , them. Nymphs . walk slowly and laboriously. Life History Time required for deve16pmeht has not been determined, but · circumstantial evidence indicates that it is one year. When 42 BULLETIN FLORIDA STATE MUSEUM Vol. 4 r6ady to emerge, nymph comes 'to surface and adult escapes. Occasionally nymph crawls out of water for emergence. In Florida, emergence begins in March and extends into early May. Farther, north, emergence is somewhat later with N. purpurea emerging in late June. In Canada, N. bicolor has been recorded in July. The time of emergence is variable, some subimag6es rising in morning, others in late ~afternoon or early evening. - Taxonomy MeDunnough, 1925. Can. Ent. 57: 168. Type species: N. bicolor MoDunnough; type locality: Laprairie, Quebec. PARACLOEODES DAY United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. abditus Day Oooxo 000 Characteristics Body streamlined. Head rounded; eyes lateral; anterolateral of Nymphs portion of he,ad deeply cut away exposing mouthparts; labial palp 2-segmented, outer apical margin -of distal segment'termi- nating in a sharp point, and inner apical margin forming a large, smoothly rounded lobe. Tarsal claws slightly curved and hooked at ends, over half as long as respective tarsi, 18-20 fine, straight denticles on inner margin of basal portion. No hind wing pad. Anterior margin of 1st tergite with a wide, deep median slot into which mesonotal scutellum fits. Seven pairs of gilts, ·all single and ovate. Three caudal filaments;,mediah filament almost as long as laterals and about equally stout; short hairs On each side of middle filament and on inner side of laterals. Body length: 4 mm. Illustration: not illustrated in full; parts in Day, 1955, Egs, 7-12. Habitat of In larger rivers,· where it is -suspected that they live in the deeper, Nymphs cooler portion until reaching maturity, when they migrate into depths of 4-6 inches near stream margins. Nymphs seem to prefer strong current where they rest on fine sand. They are warm-water species, showing remarkable ability to survive under highly marginal conditions. Type locality from which abditus , described has been dredged, diverted, and dammed, and has suffered pollution from irrigation runoff, crop dusting, sewage, and industry. Have been taken where water temperature ranges from 75-82 degrees F. Life History Length of nymphal life unknown. In laboratory emergence of subimago occurred between 8:00 and 9:00 p.m. Sometime dur- ing night subimagal molt occurred. Adults reared in August. Taxonomy Day, 1955. Pan-Pacifc Ent. 31(8): 121. Type species: P. ab- ditus Day; type locality: Tuolumne River, Stanislaus County, Caiifornia. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 43 PARALEPTOPHLEBIA LESTAGE United States Canada Species S.E. N.E. C. S.W. N.W. C. W. adoptica McDunnough X X 0 0 assimilis Banks X 0 0 0 associata McDunnough 000 bicornuta McDunnough 000 bradlevi Needham XOO brunneipennis MeDunnough 000 cachea Day 0 0 O O K O O O X X X W O O · x o K 0 0 0 0 > ~ % > 4 0 > ¢ 0 0 0 - 0 0 0 0 % 0 > < 0 0 0 > < % 0 8 0 0 0 0 '0 0 0 0 '% 0 0 0 % d < 0 0 0 0 0 0 0 0 * 0 0 0 % 0 0 0 X X X O O O K 0 0 0 0 0 0 0 0 0 californica Traver 0 0 Clara MeDunnough 0 0 debilis (Walker) o x falcula Traver o :0 georgiana Traver X 'O 0 0 0 > 4 0 '0 0 0 'O R O O K O O K O O D O . O > t o gregalis (Eaton) 6 0 0 0 0 8 0 0 0 * 0 0 0 guttata MeDunnough x o helena Day 0 0 heteronea MeDunnough o x- 0 feanae Berner o moerens MeDunnough X 'X 0 mollis (Eatdn) XX 0 0 0 0 0 0 0 * 0 > 1 0 0 0 > 4 0 0 0 * 0 0 0 0 0 . 0 ontalio MeDunnough x o packii Needham 0 0 pallipes (Hagen) 0 0 placeri Mayo · 0 .0 X 0 '0 >1 ' 0 0 0 0 0 , 0 - 0 0 . 0 0 praepedita (Eaton) 3 O 0 , quisquilia Day 0 0 6 0 fldiveliosi:. (Eaton) 0 0 0 X sculleni Traver o x 0 0 0 sticta Burks 0 0 0 00. strigula MbDunnoligh x o x o o su)annanoa Traver 0 0 0 0 0 0 temporalis McDunnough 0 0 X O 0 X vaciva'Eaton 0 0 x 000 volitans MeDunnough X O 0 X O 0 zayante Day 00 X 0.000 Characteristics Slender, body usually compressed dorso-ventrally. Head 56me- of Nymphs what depressed; eyes lateral. In a few western species, mandible greatly elongated and tuslaike, projecting anteriorly far past labrum. Tarsal claws slender, pectinate. Spinules present on apical margins of tergites 1-10. Seven pairs of narrowly lanceo- late, bifid, flamentous gms. Three caudal filaments, approxi- mately of equal length. Body length: 6410 mm. Illustra- tion: Eaton,· 1888-88, pl. 32 (as Leptophtebia); parts in Need- ham,. Traver and Hsu. 1985, Dl. XXXVII. 44 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Habitat of . Chiefly in shallow, fairly rapid streams of small to moderate size. Nymphs Often streams have bottoms of coarse gravel. Some species live among leaf debris where current is slow to moderately swift. Though mainly found here, they also occur in riffles or on large logs, sticks, and vegetation. Other species occur in rapid por- tions of swiftly flowing streams in crevices on underside of rocks. In larger shallow streams, nymphs can sometimes be found near banks On exposed roots of terrestial plants which project into water. Habits of. Awkward swimmers, moving by undulatory movements, the Nymphs wave beginning cephalically and travelling to the tails which are depressed or rai5ed as unit, When taken out of water, nymph5 move in a snake-like fashion, wriggling from side to side. Appear to be herbivores, feeding on detritus and algae. Nymphs are negatively phototropic. Life History Time required for Byniphal development Varies; in northern part of range species require a full year for development. In the extreme southern portion of range less time required, As far south as Florida nymphs may mature in 6 to 8 months. When ready to transform mature nymph crawls a short distance above water surface and after a few . moments subimago appears. Subimaginal stage may last from 12 hours in the southern forms to as much as 48 hours in northern species. In the extreme southern porti6n of range emergence occurs throughout year; however, in northern portion, emergence restricted to summer months beginning as early as May.and continuing into August. Taxonomy Lestage, 1917. Ann. Biol. Lacust. 8: 840. Type species: P. cincta (Retzius); type locality: Central Europe. PARAMELETUS BENGTSSON . United States Canada ' Species S.E.. N.E. C. S.W. N.W. C. W. chetifer Bengtsson 00000 X .O columbiae McDunnough O 0 -O X O O X 9 O O x xcroesus McDunnough 00000 0 0 midas MeDunnough 0 0 po o o o Characteristics Body streamlined. Head rounded; eyes lateral. A pincerlike of Nymphs process near the tip of the labiai palp. Tarsal claws long and slender. Gill lamellae broad, single on all segments. Three caudal filaments; middle marked heavily fringed on both sides, laterals fringed on inner side. Body length: 10-18 min. Illus- tration: not illustrated in. full; parts in Burks, 1958, fig. 280. Habitat of Live in swamps and forest pools. Water temperature of pools ' Nymphs may exceed air temperature in middle of day. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 45 Life History In Utah, eggs deposited in mid-June and remain dormant dur- ing summer and winter, hatching next May within one day.after snow m61ts. Six days after hatching, nymphs are 4-5 mm. in length and after 8 days 5-6 mrn. Nymphal_life completed with- in 16-22 days. Nymphs crawl 1 to 2 inches out of water to emerge. Taxonomy Bengtsson, 1908. Vet. Akad, Arsbok. 6: 242. Type species: P. chetifer Bengtsson; type locality: Bjorkfors, Sweden. PENTAGENIA WALSH United States Canada Species S.E. N.E. C. S.W/N.W. E. C. W. robusta MeDunnough O 0 X 0 0 0·0 0 uittigera (Walsh) OXOO OXO Characteristics Mandible with an external tusk projecting forward and visible of Nymphs from above head; tusks upcurved apically in lateral view and crenate on upper margin. Frontal process on the head bifid. Fore femora Rattened; tibiae dilated apically. Legs are fos- sorial. Seven pairs of abdominal gills, all bifid, ' First, pair of gills rudimentary, without fringes of hairs; other 6 pairs fringed laterally with long hairs that are almost as long as gills are wide. Three relatively short caudal filaments. Body length: 24 mm. Illustration: Needham, 1917-18, pl. LXXIV, fgs. 19-26. Habitat of Burrow in mud in quieter parts of larger rivers. Nymphs Life History Unknown. Nymph probably takes from 1 to 2 years to com- plete development. Adults have been taken from May to late September. Taxonomy Walsh, 1868. Proc. Ent. Soc. Philad. 2: 196. Type species: P. uittigera (Walsh); type locality: Rock Iiland, Illinois. POTAMANTHUS PICTET United States Canada Species S.E. N.E. C. S.W. N.W.. E. C. W. diaphanus Needham OX000 000 distinctus Traver XXX00 0 0 inequalis Needham OX000 0 0 mgops (Walsh) 00XOO 0 0 neglectus Traver OX000 0 0 rufous Argo O X O 0 0 0 0 oerticis (Say) XXX00 O 0 0 0 0 0 0 0 X walkeri Ide OX000 0 0 46 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Characteristics Mandibles with external tusks projecting forward and visible of Nymphs from above the head. Body of sprawling type. Frontal margin of head somewhat rounded. Mandibular tusks with short spines on dorsal surface and a few on lateral margin. Femora flat- tened, tibae and tarsi slender, long, curved spine at tip of fore tibia. Seven pairs of gills, lateral in position. Gills on 1st seg- ment·rudimentary; on segments 2-7 paired, each division slender and pointed, margins fringed with long hairs. Three, caudal ma- ments; bare at extreme base and at tip, margined with hairs elsewhere. Body length: 8-15 mm. Illustration: Burks, 1958, fig. 55. Habitat of ' ' Live on bottom amid silt and sand in rather swiftly-flowing Nymphs streams where they may be found beneath large stones in mid- stream in shallow Water. May also occur in graVel in shallow water where they sprawl on bottom. Occasionally nymphs can be found clinging to sitles of rocks. Life History Time required for development probably one year, although not determined definitely. Eggs have been hatched in the lab- pratory in 14 days. Adults have- been collected from May to mid-August. Taxon6my Pictet, 1848. Hist. Nat. 2, Ephem. Neurop. p. 208. Type ~ species: P. luteus (Linneaus); type locality: Europe. PSEUDIRON McDUNNOUGH United States Canada Species ' S.E. N.E. C. S.W. N.W. E. C. W. centralis MeDunnough OOXOOOXO meridionalis Traver X0000 000 species ? O O O X 0000 Characteristics Nymph not kn6wn with certainty. of Nymphs Life History Adults have been collected in June and July. Taxonomy MeDunnough, 1931. Can. Ent. 68: 91. Type kpecies: P. cen- tratis. MeDunnough, type locality: Lawrence, Kansas. PSEUDOCLOEON KLAPALEK United States Canada ' Species S.E. N.E. C. S.W. N.W. E. C. W. aiachua Berner x 0 0 0 0 0 0 0 anoka Daggey OOX00 000 bimaculatum Berner X0000 000 BERNER: NORTH AMERICAN MAYFLY NYMPHS 47 United States Canada Species S.E. N.E. C. S.W. · N.W. E.: C. W. carolina Banks ' XXOOOXO chlorops McDunnough O 0 0 0 0 X 0 cingulatum MeDunnough 00000 0 dubium (Walsh) x x 0 0 X 0 0 0 0 0 0 0 ~ 0 0 0 % 0 * * 0 0 ettiotti,Daggy o x o o o etowah Traver 0000 0 futile MeDunnough ' 0 0 0 0 0 ida Daggy 0 X 00 0 1 minutum Daggy OX00 0 0 0 O O K W O O C O K O X 0 0 0 O O O K 'K O O O mursum Burks OX 0 .0 0 parvulum McDunnough 0 000 0 puncticentris McDunnough O 0 0 0 0 mbrolaterate MeDunnough 0000 0 turbidum MeDunnough O 0 X O 0 ceteris MeDunnough 0 X O 0 0 ©irile MeDunnough 0 0 0 0 x 0 Characteristics Body,streamlined. Head rounded; eyes lateral; labial palp three of Nymphs segmented, distal joint rounded apically. Tarsal claws widest - at ba5e, tapering to slender tips; inner margin denticulate; each claw about 15 as long as its respective tarsus. No hind wing pads. Seven pairs of gills, single and platelike. Two well- developed caudal filaments; median filament represented by a minute rudiment. Body length: 3-6 min. Illustration:· Berner, 1950, pl. XXIV. Habitat of Typically live in shallow, fairly rapidly-flowing water in all size Nymphs streams from extremely small. trickles to large rivers. Nymphs have also been Eaken along ·margins of lakes where there is 56me wave action. Preferred habitats in smaller streams appear to be upper side of r6cks 6r other solid structures in swiftest cur- rent. S6metimes move into crevices, but mostly they are ex- posed. In swift water, where there is vegetation, the nymphs ' cling to tips of leaves where they are fully exposed to current. Often they can be found in number5 in small, pebbly riffles. Habits of Positively rheotropic; awkward swimmers. When forced to move Nymphs they swim rapidly by vigorous abdominal undulati6ns and strong lashing of caudal filaments, which are not effective propelling organs. Distance moved is extremely short. As· soon as swim- ming ceases, insect spread5 the legs. raises the tails, arches the _ back, and settles to the bottom of container. Highly adapted to living ·in swiftest waters. There has been a great increase in the relative size of the thorax and legs and a corresponding reduction of the abdomen including an almost entire disappear- ance 6f the hairs on caudal Elaments, and reduction of middle filament to a mere rudiment. Nymphs afe herbivorous. .48 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Life History Probably takes from 6 to 9 months to complete life cycle. Emergence of subimago occurs in afteinoon. Nymph comes to surface, skin splits along. dorsum, and subimago immediately rises. Subimagal stage lasts from 8 to 10 hours. In Florida adults have Been taken throughout year; in other parts of its range Pseudocloeon has more limited emergence, adults appear- ing during spring and summer months on into September. Taxonomy Klapalek, 1905. Mitt. Naturh. Mus. Hamburg 22: 105. Type species: P. kraepelini Klapalek; type locality: Buitenzorg, Java. RHITHROGENA EATON United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. amica Traver X X 0 0 anomala MeDunnough 0 0 0 brunnea (Hagen) 0 0 0 brunneotincta McDunnough 0 0 0 0 0 0 0 0 0 0 0 0 . 0 0 0 0 0 % 0 0 0 0 0 0 decopa Day 0 0 doddsi MeDunnough exilis Traver fasciata Traver jlacianula (MeDunnough) fuscifrons Traver 0 0 0 0 -- X 0 X x 0 0 '0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 '0 > 1 O O X O K > 1 0 } 0 * O K O O O K O K O O futilis McDunnough 0 ' 0 0 0 ' O O O K O C O O O o O O O K O 0 % 0 * 0 0 0 0 0 0 0 * > 1 0 0 0 0 0 * 0 0 0 0 0 0 'O O K O O C O X O O O K C X O O O O K gaspeensis MoDunnough 0 . 0 0 0 0 0 0 O X 0 0 impersonata (McDunnough) ieiuna Eaton. morrisoni (Banks) 'O pellucida Daggy o robusta Dodds 0 0 mbicunda Traver x o sanguinea Ide 0 0 uhari Tfaver x o o undulata Banks- o x b virilia MeDunnough 0 0 0 0 Characteristics Body flattene'd. Head flattened; eyes dorsal. Femora flattened, of Nymphs upper surface with many minute, spinelike processes; spines also present on margins; those on posterior margin being longer; tarsal claws short. Gills present on segments 1-7; each gill composed of ventral plate-like element and dorsal tuft of fila- ments; lamellate portions of ,lst and 7th pairs meet beneath body; margins of intermediate pairs 6verlap one another, free edge of each being deflected and pressed against surface to which nymph clings, forming an adhesive disk on venter; lamel- lae of 1st pair of gills is largest, anterior lobe much elongated; postefior lobe of 7th pair of gills elongated; 6thers more oval in 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 49 Outline. Three · caudal filaments. Body length 5-12 mm. - Il- lustration: Burks, 1958, fig. 890; Eaton, 1888-88, pl. 54. Habitat of - Live attached to stones in swift currents; often found on irregu- Nymphs larly-shaped, smooth stones and in water several inches in depth. If southeast sometimes found ih moderately r~pid streams. .. Western nymphs have been found at an elevation as high as 10,400 feet. Habits of When a rock is liftdd from water, nymphs may move quickly Nymphs from upper side· to under side or slip into a crevic6. Others may remain perfectly still until an attempt is made to remove them. Difficulty may be experienced as nymphs adhere so tightly to rocks that they can be removed without injury only with considerable care. Life History Probably one 'year required to develop from egg j to adult. Nymphs do not leave water to emerge. Mating swarms are small, occurring in late afternoon. Emergence in southern On- tario at 6:45 p.m. in early June. Adults present from May to . August. Taxonomy Eaton, 1881. Ent. Mo. Mag. 18: 23. Type species: R. semi- colorata (Curtis); type locality: Europe. SIPHLONISCA NEEDHAM United States · Canada Species S.E. N.E. C. S.W. N.W. E. C. W. aerodromia Needham OX000 000 Characteristics Body 5treamlined. Head rounded; eyes lateral. Spines present of Nymphs on the meso- and metasterna of the thorax. Lateral margins of apical, abdominal segments more or less expanded into flat, lateral extensions so that abdominal segments 5-9 are widely flaring. Gills single, very broad and platelike with abundant tracheation. Three caudal filaments, with middle one slightly shorter than the laterals. Body length 19-20 mm. Illustration: - not illustrated in full, parts in B urks, 1953, fig. 284, parts in Clemens, 1915, pl. X, figs. 1-5, pl. XI,. figs. 1-5. Habitat of Found in small, temporary pools resulting from stream over- Nymphs flow. Life Hist6ry Little known. Earliest observations of nymphs made on May 25; efnergence noted on this same day. By May.28, pool com- pletely dry, but. all nymphs emerged. Nymphs crawl from water 3-4 inches up rush stems to emerge; occurs at all hours of day, but more common in late forenoon; all emergence seems to terminate early in June. 50 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Taxonomy Needham, 1908. N. Y. St. Mus. Bull. 184: 72. Type species: S. aerodromia Needham; type . locality: Scandaga Park, New York. SIPHLONURUS EATON United States Canada Species S.E. N.E. C. S.W. N.W. C. W. alternatus (Say) O X X O autumnalis MeDunnough O 0 0 0 barbaroides ·MoDunnough O X O 0 barbus McDunnough O X O 0 columbianus Eaton 0 0 0 0 0 0 0 % 0 0 0 0 0 0 * 6 * C O X O 0 0 0 0 0 0 0 0 0 0 0 > < 0 0 0 0 0 0 ~ d K O K E O O , o o o c o c x , K x x o x . 0 , % 0 0 X 0 X decorus Traver x o o inflatus MeDunnough 0 0 0 luridipennis (Burmeister) 0 0 0 marginatuy Traver 0 0 0 marshalli Traver x 0 0 mirus Eaton 0 0 0 occidentalis Eaton 0 0 X 0 0 0 0 * O O K O X X 0 0 0 0 0 0 >€ 0 O X X X 0 X phyllis MoDunnough 0 0 x quebecensis (Provancher) 0 0 0 rapidus McDunnough x 0 0 securifer MeDunnough 0 0 0 spectabilis Traver 0 0 6 typicus Eaton x 0 0 Characteristics Body streamlined. Head rounded; eyes lateral. Tarsal claws of Nymphs long and slender. Postero-lateral angles of apical abdominal segment5 expanded into flat, lateral extensions terminating in postero-lateral spines. Gills double on abdominal segments 1 and 2 only or all 7 pairs double; large and platelike with abundant tracheation. Three caudal filaments; median filament with long hairs on both sides, lateral with hairs on inner side. Body lengtli: 9-20 mm. Illustration: Eaton, 1888-88, pl. 50. Habitat of Usually found in shallow, quiet pools along edges of streams Nymphs where they climb among the vegetation or move over the bot- tom. Sometimes found in shallow pools filled by seepage water, - on rock ledges, and in shallow pools fed intermittently with fresh water. Some species recorded from margins 6£ lakes and from vegetation in ponds. Younger nymphs of some species may be found in flowing water; mature nymphs migrate to quiet water. Habits of S. occidentatis, a pond-dwelling species, swims moderately well, Nymphs but spends most of its time half-buried in silty bottom. When disturbed swims rapidly to another place, then comes to rest on bottom. When resting can be detected by flickering move- 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 51 ments of its large gills which are in constant motion. Swims by rapidly vii*ating caudal filaments. When swimming, legs ex- tended laterally and backward in position assunied while resting on the bottom. Life History Emergence of adults from April through July. Nymphs crawl entirely out. of water to emerge. Emergence in.mornidg & early afternoon. Subimagal stage lasts from 26-58 hours. Length of nymphal life not determined; probably one year. Taxonomy Eaton, 1868: Ent. Mag. '5: 89. Type species: S. flavidus (Pic- tel); type locality: San Ildefonso, Spain. SIPHLOPLECTON CLEMENS United States Canada Species S.E, ' N.E. C. S.W. N.W. E. C, W. basale (Walker) XXX00XX costaterise Spieth X 0 0 ·0 0 O 0 interlineatum (Walsh) ,O 0 X O 0 0 X 0 0 0 0 0signatum Traver X 0 0 00 0· 0 speciosum Traver X000000 Characteristics Body streamlined. Head rounded;' eyes lateral. Tarsal claws of Nymphs of fore legs bifid; all other claws slender and longer than tibae. Gills present on abdominal segments 1-7, single and platelike on segments 4-7, double on segments 1.3, Or with small, recurved ventral flaps on gms 1-3. Three caudal filaments; middle Ela- ment with fringe of long hairs 6n both sides, lateral caudal fila- ments fringed on medfal side only.. Body length: 9-16 nim. Illustration: not illustratedin full; parts in Burks, 1958, figs. 802, 308, 805. Habitat of In slowly Rowing, larger streams where they occur close to shore Nymphs among vegetation; in water from 8-4 inches to 2 feet. Nymphs also occur at'.shores of lakes in Canada and North Carolina. Habits of Very active and vigorous swimmers if disturbed in quiet water. Nymph5 When ~attempts made. to pibk them up, they hop ab6ut like small minnows. Swim very rapidly in short spurts. Life History Unknown. Development probably takes one year. Subimagal stage in Georgia specimens required approximately 48 hours. In southpast adult specimens have been taken from late March through mid-April; farther north, adults have been taken in June, Taxonomy Clemens , 1915. Can . Ent: 47 : 258. Type species : S. basale (Walker); type: locality: Lake Winnipeg, Manitoba. 52 BULLETIN ELORIDA STATE MUSEUM Vol. 4 STENONEMA TRAVER United States . Canada Species S.E. N.E. C. S.W. N.W. E. C. W. alabamae Traver X 6 0 0 0 000 annexum Traver X O, 0 0 0 0 0 0 areion Burks O 0 X ,O 0 000 ares Burks 6 0 X 0 0 00 0 bipunctatum (McDunnough) 00 XOO XOO canadense (Walker) OXXOO X00 carolina (Banks) X.OOOXO exiguum Traver 0 0 0 000 femoratum (Say) 0 0 0 XOO frontale (Banks) 0 0 x 0 0 fuscum (Clemens) , 0 0 XOO gikiersleevei Traver 0 0 0 0 heterotarsale (MoDunnough) 0 0 0 0 * * * 0 > 4 * K X K K * O K O K · W O ,> 1 0 0 ' > 1 ·k 0 ·0 integrum (Mcbunnough) O 0 interpunctatum (Say) O 0 X ' K 0 '0 0 · 0 K C 0 * 0 ,0 * W X X K > € C O uhata (Clemens and Leonard) O 0 lepton Burks 0 > :0 0 '0 > 1 0 > 1 > 1 0 '* 0 0 0 0 0 0 0 * > 1 * > 1 0 0 > 5 ,> 1 > 5 X 0 0, X O K X O O K O X X X O O O K , K O '> 1 luteum (Clemens) 0 0 mediopunctatum (Mebunnough) 0 0 0 0 0 0 0 0 0 0 0 0 0 metriotes Burks - x o minnetonka Daggy O 0 modestum (Banks) · 6 0 0 0 0 0 _ · 0 0 0 0 0 0 - 0 0 0 0 0 0 . 0 % 0 · 0 0 nepotellum (MeDunnough) O pudicum (Hagen) 0 pulcheUum (Walsh) 0 6 0 0 0 0 0 - 0 0 1 0 0 0 0 0 0 0 0 0 0 0 rubromaculatum (Clemens) 0 0 rubrum (MeDunnough) 0 0 scitulum Traver 0 0 smithae,Tra*er 6 6 species ? o x, 0 terminatum (Walsh) x ·ox tripunctatum (Banks) x 0 6 uarium Traver 0 0 0 vicarium (Walker) X X 0 0 0 Characteristics Body flattebed. Head flattened; eyes 'dorsal. Femora flattened; of Nymphs tarsal claws short. Seventh pair of. gills reduced to slender Ela- ment Three types of abdominal gills (1) those on segments 1-6 pointed at the apexes; each gillof 7th pair with one longi- tudinal trachea; (2) first 6 pairs of gills rounded at apexes; each gill of 7th pair with l or 2 longitudinal tracheae; (8) gills on segments 1-6 truncate at :the apexes, and gills bf 7th pair with- * out tracheae. Three caudal filaments. Bbdy length: 6-20 mm. Illustration: Berner. 1950, pl. II. 1959 BERNER: NORTH AMERICAN MAYFL¥ NYMPHS 53 Habitat of May be found in varjety of situations; generally occur in mod- Nymphs erate to' swift-flowing streams of all sizes. On under surfaces of stones and rocks in streams where they tend to hifle in crevices, or on debris lodged in stream, or among leaves tkat accumulate in more slowly flowing portion of stream; occasionally in pools and backwaters. May also be found on rooted vegetation at banks of streams. Some species occur in lakes where there is some wave action near shore}. liymphs attach to debris or stones along the edge. Habits of Cling tenaciously to objects on which they live within streams. Nymphs When lifted from water, nymphs frequently scramble td under- side of rock or stick to which they are attached. Sometimes rather. difficult to detach because of their strong hold. When wdter drains away from support on which nymphs are located ' they cease moving, and detecti6n becomes rather difficult. If a little water is dashed over object, the nymphs again become active. Some reach rim of the support and drop off. Swimming is awkward, accomplished by an undulating motion of the body; swim forward only; can walk in almost any direction with equal ease. Strongly thigmatactic, If several nymphs are placed together in a dish Of water with nothing to which they may hold, form in a clump and remain thus until some other object is placed in the water with them. Desire f6r contact so strong that nymphs crawl'hito a crevice until. even the d6rsum of body ii in contact with some object. Strongly flattdned femora, and spreading legs of nymphs reduce resistance to a minimum in flowing-water habitat. Life History Time required for development has not been determined. In southeastern United States development may be completed in less than one year; in colder areas of N6rth America probably one year required. Ovipositing female flies low over water, touching surface intermittently, dropping a few eggs with each contact. Development of eggs of several species take from 11-23 days in laboratory. Total number of instars estimated to be between 40 and 45 for Stenonema canadense. Thigmotactic and phototropic responses present in nymphs upon hatching. Emergence 6ccurs while nymph floats at the surface of water; emergence takes only a few seconds; subimago appears almost immediately And Ries away. Subimagal stage lasts from 20-86 hours. Taxonomy Traver, 1988., Jour, Elisha Mitchell Sci. Soc. 48: 178. Type species: S. tripunctatum'(Banks), type 16calify: Milwaukee, Wis. - consin. 54 BULLETIN FLORIDA STATE MUSEUM Vol. 4 THRAULODES ULMER United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. arizonicus MeDunnough oooxo 000 speciosus Traver 0 0 0 X 0 0 0 0 Characteristics Body depressed. Head in South American species flattened. of Nymphs Seven pairs of double, lanceolate gills diminishing in size pos- teriorly. Postero-lateral angle5 of abdominal sigments 2-9 pro- duced as slender spines. Three caudal flaments of equal length. Illustration: not illustrated in full; parts in Traver, 1944, figs. Ed, 3,4. Habitat of Occur in streams. No observations have been made on these Nymphs nymphs in North America. Life History Adults have been collected in June and July. - Taxonomy Ulmer, 1919. Arch. Naturg. 85: 38. Type species: T. taetus (Eaton), type locality: New Granada (Columbia). TORTOPUS NEEDHAM AND MURPHY United States Canada Species ' S.E. N.E. C. S.W. N.W. E. C. W. circumfluus Ulmer O-0 X 0 -0 0 0- 0 incertus Traver X000O 000 primus (McDunnough) O 0 X O 0 .O X O Characteristics Mandibles with external tusks projecting forward and visible of Nymphs from above head. Tusks with heavy spines on outer margins; inner margin bears weak spines; lar'ge thumb-like spine proximal to tip on medial side. Frgnt of head rounded, lacking frontal process. Fore leg with the tibia somewhat flattened, fossorial. S6ven pairs of abdominal gills. First gill rudimentary and single. Other 6 pairs fully developed; margined with long flaments. Gills bilobed, each Iobe has a prominent central trachea with inconspicuous lateral branches. Three caudal filanients, median ' equal to or shorter and thinner than'laterals. Illustration: Scott, Berner and Hirsch, 1959, Egs. 3-14. Habitat of Burrow in clay banks of large rivers; in some places literally Nymphs honeycomb banks at almost everybend of river. Where bank is suitable nymphs may be located between bends. Life History Unknown. Estimated that 2 years required for development. Taxonomy Needham and Murphy, 1924: , Bull. Lloyd Lib. 24, Ent. Ser. 4:28. Type species: T. igaranus Needham and Murphy; type locality: Rio Igara-Parana, PeFU. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 55 TRAVERELLA EDMUNDS United States Canada Species ' S.E. ' N.E. C. S.W. N.W. E. C. W. albertana (McDunnough) O 0 0 X 'O 0 0 X presidiana (·Traver) OOX00 000 Characteristics Body depressed. Head rectangulhr; eyes dorsal; labrum as of Nymphs wide as head. Legs deDressed;.tarsal claws with about 12-den- ticles, those on fore legs short and wartlike, those of middle and hind legs usually well developed, PostBro-lateral corners of abdominal segments 8 and 9 developed into spines. All gills double; 1st pair largest, others diminishing in size.to gill 7; 1-5 bilamellate, each lamella witlia fmbriate margin, posterior mem- ber of each pair about % to 34 as large as anterior member. Gill 6 similar to anterior gi115 except that body of posterior member so reduced as to make gill fibrilliform. Gill 7 with both mem- bers fibrilliform, posterior member smaller. Three caudal Ela- ments; median Blament slightly longer than laterals. - Body length: 7-10 mm. Illustration: Edmunds, 1948, pl. V, figs. 8-15, pl. VI. Habitat of In rapids of medium-sized to large streams, where nymphs may Nyinphs be f6und on underside of rocks. On some rocks nymphs occur in large numbers, more than a hundred.being found per square foot of surface. Life History - Observations have only been made on T. albertana. Emergence occurs in late August and probably through September. Sub- imagoes begin emergence at about 7: 10 p.m. when light in- tensity reduced to approximately 5 foot candles. Great ma- jority of individuals emerge within 20 minutes of this period, followed by an abrupt cessation as light intensity dropped to less than »1 foot candie. Taxonomy Edniunds, 1948. Proc. Bid. Soc. Wash. 61: 141. Type species: T. albertana·(MeDunnough); type locality: Medicine Hat, Alberta. TRICORYTHODES ULMER United States Canada Species S.E. N.E. C. S.W. N.W. E. C. W. albilineatus Berner X00 0000 allectus Needham OXO O 000 0 0 0 X atratus MeDunnough, 00 X 0 X00 explicatus (Eaton) 00 X 0 000 56 BULLETIN FLORIDA STATE MUSEUM Vol. 4 United Sfates Canada Species S.E. N.E. C. S.W. N.W. E. C. W. fallax Traver OXOXX XXO fictus Traver OOXOO 000 minutus Traver oooxo oox peridius Burks OOXOO 000 stygiatus MeDunnough O O X O O X O. O texanus Traver OOXOO 000 Characteristics Short, stout. Head rounded; eyes lateral; apical margin of of Nymphs lai*ilin rather deeply notched at median line. No hind wing pads present. Legs relatively long; tarsal claws long and ho6ked at apex. Gills present on abdominal segments 2-6, those on 2 subtriangular and operculate; segments 8-6 with a pair of double, platelike gills, each has the margins entire. Three caudal fila- ments which are relatively long and stout and have a whorl of setae at each articulation. Body length: 8-7 mm. Illustration: Bemer, 1950, pl. XV. Habitat of In streams which have at least a perceptible current. May be Nymphs found amid fine sand and gravel on stream beds or in moss or other plant growth on large stones; sometimes at bank near - bases of rooted vegetation or among exposed, washed roots - of terrestial plant5. All streams from which nymphs have been taken are permanent, varying in size from rather small creeks to Jarge rivers. Habits of Principally herbivores. Awkward swimmers; undulatory action Nymphs of abdomen produces forward movement. Seldom swim; move almost entirely by crawling. Life History Time required for nymphal development not determined; but in southern portion of range, probably less than one year. When ready to emerge nymph comes to surface, and subimago imme- diately bursts free. Emergence occurs after dark in some species or in very early hours of morning in others. At time of emerg- ence large number of adults come out simultaneously. Length of subimaginal stage not determined, but very b-def. In south- eastern position of range, especially in.Florida, emergence occurs from February to October; farther north the period of emergence fr6m May to August. Some species of Tricorgthodes are said to shed subimaginal skin while in flight; however, this point is in dispute. The general jmpression is that adults alight to molt. Taxonomy Ulmer, 1920. Stett. Ent. Zeit. 81: 122. Type species. T. expli- earns (Eaton); type locality: North Sonora, Mexico. 1959 BERNER: NORTH AMERICAN MAYFLY NYMPHS 57 SELECTED REFERENCES ~ Berner, Lewis 1950. The mayflies of Florida. University of Florida Press, Gainesville. Bio. Sci. Ser. xii + 267* 88 figs.,*24 pls, 19 maps. 1955. The southeastern species of Baetisca (Ephemeroptera: Baetiscidae). Quart. Jour. Fla. Acad. Sci. 18(1). 1-19,.23 figs. 1956. The genus Neoephemera in North America (Ephemeroptera: Neoephem- eridae). Ann. Ent. Soc. Amen 49(1): 88-42,26 figs. Burks, B. D, 1958. The mayffies, or· Ephemeroptera, of Illinois. Bull, Ill. Nat. Hist·. Survey. Vol. 26, Art. 1, 1-216, 895 figs. Clemens, W. A. 1915. Mayflies of the Siphlonurus group. Can. Ent. 47: 245-260, pl. 9-11. Day, W. 'C. 1955. New genera of mayflies from California ·(Ephemeroptera). Pan-Pacific Ent. 31(3): 121-137, pls. I-V. 1956. Ephemeroptera. (Chap. 8 in Aquatic insects .of, California. R. L. Using- er, Ed., U. of Calif. Press. Berkeley) p. 79-105, 28 figs. Eaton, A. E. 1888-88. A revisional monograph of recent Ephemeridae or mayflies. Trans. Linn. Soc. London. Sec. Ser. Zool. Vol. 8, pA 1-852, 65 pls. Edmunds. G. F., Jr. 1948. A. new genus of mayflies from western North America (Leptophlebiinae). Proc. Biol. Soc: WaAh. 61: 141-148, pl. V-VI. , 1951. New species of Utah mayflies. I. Oligoneuriidae (Ephemeroptera). Proc. Ent. Soc. Wash. 58(6): 327-331, pl. 41. Edmunds, G. F., and R. K. Allen 1957. A checklist of. the Ephemeroptera of, North America north of Mexico. Ann. Ent. Soc. Amer. 50(4): 817-824. Edmunds, G. F., Jr., L. Berner, and Jay R. Traver 1958. North American mayflies of the family Oligoneuriidae. Ann. Ent. Soc. Amer. 51(4): 875-882, 81 figs. Edmunds, George F., Jr., and Jay R. Traver 1959. The classification of the Ephemeroptera I. Ephemeroidea: Behninglidae. Ann. Ent. Soc. Amd. 52(1): 48-51, 82 figs. Hunt, B. P. 1958. The life history and economic importance of a burrowing mayfly, Hexa- genia limbata, in southern Michigan lakes. Bull. Inst. for Fish. Res., Mich. Dept. Conserv. no. 4. 151 p., 45 figs., 62 tabs. 58 BULLETIN FLORIDA STATE MUSEUM Vol. 4 Ide, F. P. 1985. The effect of temperature on the distributipn of the mayfly fauna of a stream. Univ, of. Toronto Studies, Biol. Ser, 89, Pub, Orit: Fish. Res. Lab, 50.9-76, Dls, 1-10. MeDunnough, J. 1981. The bicolor group of the genus Ephemerella, with particular reference to the nymphal stages. Can. Ent, 68.30-42, 61-68, pls, 2-5, 1931. The eastern North American species of the genus Ephemerella and their nymphs. Can. Ent. 68: 187-197, 201-216, pls. 11-14. 1988. The nymph Of Cint/gma integrum and description of a new Heptagenine ' genus. Can. Ent. 65: 78-76, pl. 2-3. Needham, J. G. - 1921. Burrowing mayflies of our larger. lakes and streams. .U.S. Bur. Fish. Bull. for 1917-18. 36: 265-292, pls. 70-82. Needham, J· G., and Helen E. Murphy 1924. Neotropical mayflies. Bull. Lloyd Lib. no. 24. Ent. Ser. 4: 1-79, pls. 1-18. Neewham, J. G., J. R. Traver, and Yin-Chi Hsu 1985. The biology of mayflies with a systematic account of North American species. Comstock Pub. Co., Ithaca, xvi + 759, 40 pls., 168 figs. Pennak, R. W. 1958. Fresh-water ihvertebrates of the United States. Ronald Press Co., New York. ix, + 7.69 p., 470 fgs. Scott, D. C., L. Berher, and A. Hirsch 1959. The nymphs of the mayfly genus Tortopus (Ephemeroptera: Polymi- tarcidae). Ann. Ent. Soc. Amer. 52(2): 205-213, 14 figs. Spieth, H. T. 1941. Taxonomic studies on the Ephemeroptera. II. The genus Hexagenia. Amer. Mid. Nat. 26: 283-280, 50 figs., 12 maps. 1947. Taxonomic studies on the Ephemeroptera. IV. The genus Stenonema. Ann. Ent. Soc. Amer. 40(1): 87-122, figs. 29-31, pls. 1-2. Traver, Jay R. 1982-88. Mayfies of North Carolina. Jour. Elisha Mitchell Sci. Soc. 47(1): 85-161, pls. 5-12, (2): 168-236, 48(2): 141-206, pl. 15. 1944. I. Notes on Brazilian mayflies. Boletim do Museu Nacional-Zool. No. 22: 2-58, 20 figs. Walley, G.· S. 1980. Review of Ephemerella nymphs of western North America. Can. Ent. 62: 12-20, pls. 1-3. Contributions to the BULLETIN OF THE FLORIDA STATE MUSEUM may be in any field of biblogy. Manuscripts dealing with natural history or systematic problems involving the southeastern United States or the Caribbean area are solicited especially. Manuscripts should be of medium length-42 to 200 printed pages. Examination for suitability is made by an Editorial Board. The BULLETIN is distributed worldwide through institutional subscriptions and exchanges only. It is consider6d the responsibility of the author to distribute Ris paper to all interested individuals. To aid in thi5, fifty copies are furnished the author without cost. PREPARATION OF MANUSCRIPT Highly recommended as a guide is the "Style sheet for the scientific serial publica- tions of the American Museum of Natural History," second edition, revised, 1958. 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