Bulletin lJi I ILLINOIS S'aitii.ara.1 History BULLETIN S"u.i:»"vey Larvae of the Sericothripini (Thysanoptera: Thripidae), with Reference to Other Larvae of the Terebrantia, of Illinois imas C. Vance \". OF ILLINOIS iPVRTMENT OF REGISTRATION AND EDUCATION ^'URAL HISTORY SURVEY DIVISION tANA, ILLINOIS rHE UBRftRY OF. THE OCT 11974 JNi.crtsHY Oh IU-INOIS AT URBANA-CHAMPAIGH VOLUME 31, ARTICLE 5 AUGUST, 1974 ILLII^OIS a.tura.1 Histo]:*3r Sur^vey BULLETIN Larvae of the Sericothripini (Thysanoptera: Thripidae), with Reference to Other Larvae of the Terebrantia, of Illinois nas C. Vance OF ILLINOIS RTMENT OF REGISTRATION AND EDUCATION URAL HISTORY SURVEY DIVISION ^NA, ILLINOIS VOLUME 31, ARTICLE 5 AUGUST, 1974 STATE OF ILLINOIS DEPARTMENT OK REGISTRATION AND EDUCATION BOARD OF NATURAL RESOURCES AND CONSERVATION Dean Babbixuer, Ph.D., Chairman; Thomas P.uik, Ph.D., Biology; L. L. Sloss, Ph.D., Geology; Heiibebt S. Gdtowskv, Ph.D., Chemistry; Robert H. Anherson, B.S.C.E., Engineering; Charles ¥.. Olmsted, Ph.D., Forestry; W. L. Evbritt, E.E., Ph.D., Representing the President of the University o/ Illinois; Elbert 11. Hadlet, Ph.D., Representing tlie President of Southern Illinois University. NATURAL HISTORY SURVEY DIVISION, Urbana, Illinois SCIENTIFIC AND TECHNICAL STAFF Gborge Sprugel, Jr., Ph.D., Chief Alice K. Adams, Secretary to the Chief Section of Economic Entomology AViLLiAM II. LucKMANN, Ph.D., Eutomologist and Head Willis N. Bruce, Ph.D., Entomologist AVayne L. Howe, Ph.D., Entomologist Stevenson Moore, III, Ph.D., Entomologist, Extension Howard B. Petty, Ph.D., Entomologistj Extension James E. Appleby, Ph.D., Associate Entomologist Edward J. Armbrust, Ph.D., Associate Entomologist Marcos Kouan, Ph.D., Associate Entomologist Joseph V. Maddox, Ph.D., Associate Entomologist Ronald H. Meyer, Ph.D., Associate Entomologist Robert D. Pausch, Ph.D., Associate Entomologist Ralph E. Sechriest, Ph.D., Associate Entomologist John K. Bousejian, M.S., Assistant Entomologist George L. Godfrey, Ph.D., Assistant Entomologist William G. Ruesink, Ph.D., Assistant Entomologist James K. Sanborn, Ph.D., Assistant Entomologist Douglas K. Sell, Ph.D., Assistant Entomologist John L. Wedbebg, Ph.D., Assistant Entomologist Clarence E. White, B.S., Assistant Entomologist Keun S. Park, M.S., Assistant Chemist Sue E. Watkins, Supervisory Assistant Donald E. Kuhlman, Ph.D., Assistant Professor, Extension RoscoE Randell, Ph.D., Assistant Professor, Extension Tim Coolet, M.A., Assistant Specialist^ Extension Kurt E. Rbdborg, M.S., Assistant Specialist John F. Walt, M.S., Assistant Specialist, Extension Jean G. Wilson, B.A., Supervisory Assistant Daniel P. Bartell, Ph.D., Research Associate Martha P. Nichols, M.S., Research Associate Robert J. Barney, B.S., Research Assistant Tzu-SuAN Chu, M.S., Research Assistant Stephen D. Cowan, B.S., Research Assistant Stephen K. Evrabd, B.S., Research Assistant Barbara J. Ford, M.A., Research Assistant Ray.mond a. Kotek, M.Mus., Research Assistant Rose Ann Meccoli, B.S., Research Assistant Barbara E. Peterson, B.S., Research Assistant Ketukah Reinbold, M.S., Research Assistant Stephen Roberts, B.S., Junior Professional Scientist John T. Shaw, B.S., Junior Professional Scientist Lowell Davis, Technical Assistant Charles G. Helai, M.S., Technical Assistant Linda Isenhower, Technical Assistant Lu-PiNG LeEj M.S., Technical Assistant Section of Botany and Plant Pathology Robert A. Evehs, Ph.D., Botanist Eugene B. Himelick, Ph.D., Plant Pathologist R. Dan Neely, Ph.D., Plant Pathologist D. F. Schoeneweiss, Ph.D., Plant Pathologist J. Leland Crane, Ph.D., Associate Mycologist Walter Hartstirn, Ph.D., Assistant Plant Pathologist Betty S. Nelson, Junior Professional Scientist Gene E. Reid, Technical Assistant Section of Aquatic Biology D. Homer Buck, Ph.D., Aquatic Biologist William F. Childers, Ph.D., Aquatic Biologist R. Weldon Larimore, Ph.D., Aquatic Biologist Robert C. Hiltibran, Ph.D., Biochemist Allison Brigham, Ph.D., Assistant Aquatic Biologist Warren U. BnHiHAM, Ph.D., Assistant Aquatic Biologist RiCH.\RD E. Sparks, Ph.D., Assistant Aquatic Biologist John Tranquilli, M.S., Assistant Aquatic Biologist Donald W. Dufford, M.S., Junior Professional Scientist Mary Frances Martin, Junior Professional Scientist John M. McNurney, M.S., Junior Professional Scientist Ted W. Storck, Ph.D., Junior Professional Scientist Richard J. Baur, M.S., Research Assistant Tom Hill, M.S., Research Assistant Richard Kocher, B.S., Research Assistant Robert Moran, M.S., Research Assistant C. Russell Rose, Field Assistant Section of Faunistic Surveys and Insect Identification Philip W. Smith, Ph.D.. Tazononn'st and Head Wallace E. LaBerge, Ph.D., Taxonomist Milton W. S.\nderson, Ph.D., Taxonomist Lewis J. Stannard, Jr., Ph.D., Taxonomist Larry M. Page, Ph.D., Assistant Taxonomist John D. Unzicker, Ph.D., Assistant Taxonomist Donald W. Webb, M.S., Assistant Taxonomist Bernice p. Sweeney, Junior Professional Scientist Section of Wildlife Research Glen C. Sanderson, Ph.D., Wildlife Specialist and Head • Frank C. Bellrosb, B.S., Wildlife Specialist Jean W. Graber, Ph.D., Wildlife Specialist Richard R. Graber, Ph.D., Wildlife Specialist Harold C. Hanson, Ph.D., Wildlife Specialist Ronald F. Labisky, Ph.D., Wildlife Specialist William L. Anderson, M.A., Associate Wildlife Specialist W. W. Cochran, Jr., B.S., Associate Wildlife Specialist' William R. Edwards, M.S., Associate Wildlife Specialist' G. Blair Joselyn, M.S., Associate Wildlife Specialist Charles M. Nixon, M.S., Associate Wildlife Specialist KeNxNETH E. Smith, Ph.D., Associate Chemist Ronald L. Westemeier, M.S., Associate Wildlife Specialist Stephen P. Havera, M.S., Assistant Wildlife Specialist t David R. Vance, M.S., Assistant Wildlife Specialist Ronald E. Duzas, Junior Professional Scientist Helen C. Sciiultz, M.A., Junior Professional Scientist Eleanore Wilson, Junior Professional Scientist Sharon Fradenburgh, B.A., Laboratory Technician Robert D. Crompton, Field Assistant James W. Seets, Laboratory Assistant Section of Administrative Services Robert O. Watson, B.S., Administrator and Head Supporting Services Vernon F. Billman, Maintenance Supervisor Wilma G. DiLLMAN, Property Control and Trust Accounts Patty L. Duz.\n, Technical Assistant Robert O. Ellis, Assistant for Operations Larry D. Gross, Maintenance Supervisor Lloyd E. Huffman, Stockroom Manager J. William Lusk, Mailing and Distribution Services Mblvin E. Schwartz, Financial Records James E. Sergent, Greenhouse Superintendent Publications and Public Relations Owen F. Glissendorf, M.S., Technical Editor Robert M. Zewadski, M.S., Associate Technical Editor Shirley McClellan, Assistant Technical Editor Lawrence S. Farlow, Technical Photographer Lloyd LeMere, Technical Illustrator Technical Library Doris F. Dodds, M.S.L.S., Technical Librarian Doris L. Sublette, M.S.L.S., Assistant Technical Librarian CONSULTANTS AND RESEARCH AFFILIATES : SVstematic Entomology, Roderick R. Irwin, Chicago, Illf ' noisj Wildlife Research, Willard D. Klimstra, Ph.D., Professor of Zoology and Director of Cooperative WilO- I •' ~ ~ " Norman D. Levine, Ph.D., Pmfvssor of Veterinnr*' u- of the Center for IJumon Erufuqi/, Ihrirrr.-^Hi/ of Zuuloijii an.l of Entumologi, tuul llnul of Ihr [\ WaLDBAURR, I'h.n.. Prnfrssur of Enlunnilo;/,,. I 'rofcssor uf Statistical Design and Analysis, Vniien life Research, Southern Illinn CONTENTS Acknowledgments 145 Materials and Methods 146 Analysis of Charactebs 147 Color 148 Antennae 148 Head and Pronotum 149 Terminal Abdominal Segments 149 Setae 149 Cuticle 149 Metamorphosis 149 Life History of Sericothrips Variabilis ( Beach ) 150 Methods 150 First-Instar Lai-va 151 Second-Instar Larva 152 Prepupa 152 Pupa 153 Adult 153 Effect of Temperature and Photoperiod on Development 153 Site of Pupation 154 Mating 154 Predators 155 Economic Assessment 155 Phylogeny 156 Phylogeny of the Thysanoptera 157 Phylogeny of the Tribes of the Thripidae 159 Phylogeny of the Sericothripini 163 Systematics 166 Literature Cited 204 Index 207 TMs report is printed hy authority of the State of Illinois. IRS Ch. 1%T, Par. 58.12. It is a contribution from the Section of Faunistic Surveys and Insect Identification of the Illinois Natural History Survey. Thomas C. Vance is employed by the Illinois Department of Conservation as a Site Interpretive Specialist at Lincoln Log Cabin State Park, Lerna, Illinois. (68199—2M—8-74) Frontispiece.—Larva I (lower left) and larva II (upper right) of Sericothrips pulchellul i Hood on its host, wafer ash (Ptelea sp.) . (Photographs by Lawrence S. Farlow) Larvae of the Sericothripini (Thysanoptera: Thripidae), with Reference to Other Larvae of the Terebrantia, of Illinois The morphology and taxonomy of the immature stages of the Thysanoptera have received minimum attention in North America. Significant contribu- tions on the larvae of thrips have been made in Europe, East Asia, and North Africa (Priesner 1926fl, 1926Zj-192S, and 1960) and in India (Jagadish & Ananthakrishnan 1972), and these studies constitute the basis of our knowledge. In the United States most of the descriptions of the immature stages are found in accounts of the life histories of economically important thrips. This report deals mainly with the second-stage larvae, especially the known forms belonging to the tribe Sericothripini as represented in Illinois, and includes a comparison of the larval characteristics of many of the genera of the suborder Terebrantia that are found in the same region. Larval char- acteristics were used to substantiate the classification formerly based on adult features and to interpret the phylogeny of this insect order. A special study on the life history of Seiicothrips vari- abilis (Beach) was included to provide an example of the bionomics of a com- mon species. References to the literature, with few exceptions, terminated in 1971 when this report was submitted as a Master of Science thesis to the Department of Entomology, University of Illinois, Ur- bana. ACKNOWLEDGMENTS Support for this work was provided by the Illinois Agricultural Experiment Station, Project S-74, Biology and Con- Thomas C. Vance trol of Arthropods on Soybeans, and by the Illinois Natm-al History Survey. I thank all those who have helped in the preparation of this report. I am particularly grateful to Dr. Lewis J. Stannard, Jr., for many suggestions and continued help throughout the course of this study and to Dr. Bruce S. Heming for additional advice and in- formation, especially on the tentorium and other morphological features. Ap- preciation is extended also to Dr. Wil- liam H. Luckmann, Illinois Natural History Survey, for arranging financial support; to Lloyd L. LeMere, Survey Technical Illustrator, for drawing Fig. 1-5; to Wilmer D. Zehr, former Tech- nical Photographer of the Natural His- tory Survey, and Lawrence S. Farlow, present Survey Photographer, for photo- graphic reproductions of the figures; and to many other staff members at the Survey for their assistance and kindness. Further, I wish to thank my former associate. Dr. Thomas H. Wilson, for help and consultation on many prob- lems, and my wife, Susan, for construc- tive criticism. Most of the material studied was from the collection of the Illinois Natu- ral History Survey. Additional speci- mens were lent to me through the gen- erous cooperation of Miss Kellie O'Neill, U.S. Department of Agriculture, and Dr. Tokuwo Kono, California Depart- ment of Agriculture. The manuscript was edited for pub- lication by Robert M. Zewadski, As- sociate Technical Editor, Illinois Natu- ral History Survey, and reviewed by Dr. Bruce S. Heming, Associate Profes- sor, University of Alberta, and Dr. Lewis J. Stannard, Jr., Illinois Natural 145 146 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 Hi.stoi-y Survey Taxonomist and Pro- fessor of Entomology, University of Illi- nois. The typing and proofreading of the manuscript were done by Mrs. Bernice Sweeney and Mrs. Grace Fin- ger, Illinois Natural History Survey. MATERIALS AND METHODS During this study about 500 im- mature thrips were examined. In addi- tion, diagnostic features were analyzed froin descriptions of immatures in the literature, the reference being cited in each case. Repositories and institutions are identified in the Material-Examined sections by these abbreviations: INHS = Illinois Natural History Survey collection USNM = United States National Mu- seum (National Museum of Natural History, Smith- sonian Institution) Three methods were used in collect- ing immature thrips. Large plants were sampled with a black sweep net (to make the light-colored immatures more visible), the thrips being recovered from the net with the aid of a hand lens and a small camel hair brush. Branches were shaken over a piece of cardboard or other material from which the thrips were recovered. Small host plants were sampled by examining individual leaves, and the thrips were removed directly from the leaf surfaces. The preserving solution used was AGA (eight parts 95-percent ethanol, five parts distilled water, one part glyc- erine, and one part acetic acid ) , which kept the body soft and facilitated spreading of the appendages. For stor- age beyond 4 weeks, thrips were trans- ferred to 70-percent ethanol. Both Canada balsam and Hoyer's medium were used in making whole mounts. Canada balsam is a permanent mounting medium (Hartwig 1952; Pries- ner 1960; Stannard 1968), which pre- serves the color and featiores of thrips well, but it is difficult to use and much time is required to make good prepara- tions. Further, because of dehydration and accompanying brittleness, speci- mens can be damaged during mount- ing in Canada balsam, and small setae, microtrichia, cuticular sculpturing, and areas of light brown coloration often are obscured. Hoyer's is easier to use and renders visible many diagnostic features not usually seen on specimens mounted in balsam. Unfortunately, Hoyer's, a water-base medium, usually crystallizes within a few years. Specimens for the permanent collection, therefore, were mounted in Canada balsam, but some of each series were mounted in Hoyer's medium for temporary study. Balsam mounts were prepared in a manner similar to that described by Heming (1969). Larvae and adults were transferred from AGA to 70-percent ethanol and were then passed succes- sively through 95-percent ethanol, ab- solute ethanol, and absolute ethanol and clove oil, remaining in each solu- tion for about one-half hour. Specimens were then placed in a small Syracuse watch glass containing pure clove oil; when each sank to the bottom, it was transferred to a sUde. Clearing in 10- percent KOH or NaOH was usually un- necessary for immatures except to dis- solve the excessive amounts of fat body found in some larvae. In mounting, each thrips was placed ventral side up in a small drop of dilute balsam on a cover slip held in place on a small cardboard stage. The appendages were spread, and two chips of cover glass were added to the balsam. These chips prevent crushing of the specimen by the cover slip as the balsam dries. A small drop of balsam was placed in the center of a microscope slide, and the slide was in- verted and placed gently upon the cover slip. When the slide was lifted and turned right side up, the cover slip and specimen adhered to it. Slight pressure applied to the cover shp with August, 1974 Vance: L.\rvae of the Sericothripini 147 an insect pin spread the appendages farther. Whole mounts in Hover's medium were prepared in the same way, but the dehydration schedule was omitted. Most Hoyer preparations in the Survey collection deteriorated after a few years, even when ringed with Zut Slide Ringing Compound (Bennett's Paint Products, Salt Lake City) or clear fin- gernail polish. However, some prepara- tions ringed with fingernail polish have remained in good condition for more than 20 years, indicating that efficient ringing compounds might prove suc- cessful in preserving Hoyer mounts. Bright-light microscopes were used throughout this study except when minute structures, such as microtrichia, \\'ere being observed, for which work phase-contrast microscopes \\'ere em- ployed. ANALYSIS OF CHARACTERS According to Priesner (1960) "the shape of the antennal segments, tlie sculpture of the body cuticle, the chaetotax}', and last but not least, the colour, are important" in taxonomic study of larval thrips. These characters and certain others were the principal ones used in this investigation. Many characters varied with the stage of larval development, particularly color, many body dimensions, and cuticular sculpturing, which vary with growth and instar. Color also varies with the type of food consumed by tlie larvae. Different characters have been used in this study according to the taxonomic level concerned. In classifying thrips larvae at the family level, the form and shape of the antennal segments and the presence or absence of modified spines on the ninth abdominal tergite are im- portant in making distinctions. At the subfamily level, the form of certain antennal segments is important. Many charai'ters at the tribal level were found to intergrade, but certain features could generally be assigned to each tribal group. Members of subtribal groups tended to exhibit a greater degree of similarity and could be assigned to the proper group with less difficulty. The greatest stabilization of charac- ters occurs at the genus level. Most genera are sharply delimited, and even closely related genera usually exhibit diagnostic differences. One exception occurred in the tribe Thripini in which the larvae of the Frankliniella-Thrips- Taeniothrips complex are cjuite similar. Important generic characters include cuticular sculpturing; microtrichia; setal type, length, and placement; coloration; and proportions and features of the antennal segments. Little distinction was found at the species level, closely related species often being nearly alike in fonn. Species differences that were found include the length and proportions of the body setae, brown sclerotized areas, setal basal rings, and cuticular and hypo- dermal coloration in mature larvae. Ward (1968) found that slight consist- ent differences are present in larvae of several closely related species of Thrips and that, despite their subtlet}', these characteristics can be used to separate these species with confidence. Most of the characters mentioned above apply to second-instar larvae; in first-instar larvae few diagnostic characters occur at the generic level and none were detected at the spe- cific level. At the family and subfamily levels first-instar larvae may be recog- nized by the same antennal characters distinguishing second-instar larvae. At the tribal and subtribal levels the pat- tern of microtrichia on the antennae and general body and antennal features are useful in making distinctions. The prepupal and pupal instars show little interspecific variation. According to Priesner (1960), tlie only distinguish- ing characters are the presence or ab- sence of cuticular spines near tlie apex of the abdomen and the shape of the antennae. The taxonomic value of these 148 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 features above the species level may be questionable, since Priesner (1960) reported one species of Taeniothrips with spines and another species of the same genus without them. COLOR Four types of coloration occur in thrips larvae: (1) that of the internal organs and body contents, (2) that of the cuticle, (.3) that of underlying hypo- dermal pigmentation, (4) and areas of brown sclerotization on the cuticle sur- face. Because color varies with the de- gree of larval development, it is best to deal only with fully mature larvae. The colors of internal organs and body contents depend upon the food ingested. Phytophagous larvae often appear green due to the ingestion of chlorophyl, and predacious larvae may assume the color of the prey ingested. Such colors are usually leached out dur- ing the mounting process and are prac- tically useless for taxonomic purposes. Cuticle color among specimens of the same species varies from white to yellow to orange. These pigments can be affected by the mounting media used, and are leached out with pro- longed storage in alcohol. Underlying hypodermal pigmenta- tion is usually not affected by mounting media but does vary greatly even in the members of a series of specimens. Some species never show hypodermal pigmentation, while in others it is usu- ally present in some members of a series of specimens. Hypodemial pig- mentation is susceptible to leaching with prolonged storage in alcohol al- though at a slower rate than is cuticular coloration. Brown sclerotized areas, such as cer- tain antennal segments, areas of the head and thorax, and areas of the terminal abdominal segments, are the most dependable color features. Dis- tinctive brovm sclerotized areas are particularly valuable in the identifica- tion of many species of the Helio- thripinae, Anaphothripini, and Chiro- thripini. This brown color does not vary much within a species, is not leached with prolonged storage in al- cohol, and is not affected by mounting media although these light brown areas may be difficult to see in balsam. ANTENNAE Antennal features are the most re- liable characters in the taxonomy of larval thrips. Lengths of segments and the number of annulations present are important at the family and subfamily levels, whereas the shapes of the seg- ments and the nature of their annula- tions and microtrichia can be diagnostic of genera and higher groups. The microtrichia of antennal segments III and IV and the shapes of the terminal segments are often diagnostic in first- stage larvae of certain groups. Larval members of the Sericothripini, for ex- ample, tend to have narrowed, tapering, seventh antennal segments and dense, random microtrichia on segment IV. However, members of some other tribes have broader seventh segments, and few have microtrichia on segment IV except on the annulations. Antennal sense cones are of diag- nostic value at the generic and higher levels. The length of sense cones in adult Thysanoptera often varies, but in the larvae it seems fairly stable. In general, the primitive families (Aeolo- thripidae, Merothripidae, and Hetero- thripidae) and the tribes Chirothripini and Thripini tend to have shorter sense cones, and the Anaphothripini, Serico- thripini, and Dendrothripini have longer ones. The sense cones on seg- ments IV, V, and VI are the best de- veloped and therefore are used for taxonomic analysis. The entire antennae of some genera are diagnostic (such as those of Chiro- thrips, which has greatly reduced an- tennae); features of the entire anten- nae, however, often show little dif- ferentiation at the generic level. August, 1974 V.\NCE: Larvae of the Sericothripini 149 HEAD AND PRONOTUM The shape and size of the head and pronotum are distinctive and diagnostic of certain genera of thrips larvae. These features include the ratio of length to width, shape, size of eye facets, degree of bulging of the eyes, and degree of constriction at cheek margins. Small, nonbulging eye facets occur in the Chirothripini, and construction of the cheeks seems to be characteristic of the Heliothripinae and some Anapho- thripini. Problems associated with the head and pronotum include distortion due to pressure from the cover slip and dif- ferences in their degree of development within the larval stage. TERMINAL ABDOMINAL SEGMENTS The shape of the terminal abdominal segments differs between the suborders Terebrantia and Tubulifera. In the Thripini and in Anaphothrips a pos- terior comb is present on abdominal segment IX. According to Priesner (1960), each species has a characteristic form of this comb. SETAE The type and length of body setae are important features in larval dif- ferentiation. Setae vary in length and type above the generic level; however, they are useful in the diagnoses of genera. Setal t)'pes, as listed by Pries- ner (1960:66-67), are: pointed! lance- olate, blunt or rounded, knobbed, fun- nel-shaped, forked or fringed, and spoon-shaped or fanned. Their lengths may vary from less than 5 //m up to 70 itm, and they may be slender or stout. Each genus has characteristic types and lengths of setae. Setae differ in their widths and lengths between species, and certain setae differ in their proportionate lengths. The degree of development of the bro\\'n rings at the bases of the setae can be important diagnostic fea- tures. Some variation in the setae oc- curs between individuals; the lengths, however, do not change with the degree of development. CUTICLE The presence and nature of cuticular pustules and cuticular microtrichia pro- vide good diagnostic characters at the generic and subtribal levels. Micro- trichia are long to short, depending on the species. Short microtrichia are al- most invisible when viewed through a light microscope and appear as a stip- pling effect. They are sparsely to densely scattered over the integument. Pustules are minute to large, depending on the species, and usually each pustule bears one microtrichium although the large pustules of the Anaphothripini and Heliothripinae lack microtrichia. Cuticular features which are stable at the generic level present some prob- lems. Small pustules and microtrichia are often difficult to see in balsam mounts and can be distorted by the mounting process. Also, cuticular sculp- turing varies with the degree of larval development and abdominal distension. METAMORPHOSIS In the Terebrantia there are usu- ally four immatm"e stages, the first- and second-instar larvae, the prepupa (propupa), and the pupa. In the Tubu- lifera, by contrast, an additional pupal instar occurs, resulting in a total of five stages. Larval stages lack wings or wing pads and have free antennae, and active movements and feeding take place. The prepupal and pupal stages are quiescent and do not feed. Tlieir antennae lack segmentation and are di- rectly forward in prepupae and are bent back dorsally (Terebrantia) or laterally (Tubulifera) along the head in pupae. Wing pads are usually present in prepupae and pupae of the Terebrantia but only in the pupal stages of the Tubulifera. Each stage is tenninated 150 Illinois Natuhal History Survey Bulletin Vol. 31 Art. 5 by a molt, with the exuviae usually left on the leaf surface. Thrips are usually recognized as exopterygote insects and are placed with the hemipteroid orders even though their postembryonic develop- ment more closely resembles the holo- metabolous transfonnations found in the Endopterygota. This intermediate type of development in the Thysanop- tera has caused considerable contro- versy, some authors calling the im- matures nymphs and others calling them larvae and pupae. Takahashi (1921) even proposed the term "Reme- tabola" for thysanopteran metamorpho- sis. Recent histological studies on the postembryonic development of the Thysanoptera have provided insights into the problem. Davies (1961) found that the development and adult mor- phology of the female reproductive or- gans of Limothrips cerealium showed similarities to the exopterygote insects but that their delayed development recalled endopterygote morphogenesis. This conclusion is supported by Hem- ing (1970) in a similar study on Frank- liniella fusca (Hinds) and Haplothrips verbasci (Osbom). Davies (1969) stud- ied the metamorphosis of the skeletal musculature of L. cerealium and found many details of myogenesis in the pupae of thrips to be similar to those in the pupae of endopterygote insects. He stated that "thysanopteran ontogeny shows histological changes at least as great as those in the holometabolous metamorphosis of many Endopterygota and these quiescent instars are per- fectly entitled to rank as pupal stages." Davies further hypothesized that the holometabolous type of metamorphosis in the Tliysanoptera developed inde- pendently of that of the Endopterygota and speculated about the selective value of two or three pupal stages in the Thysanoptera when only one is usually necessary for similar trans- formations in the Endopterygota. LIFE HISTORY OF SERICOTHRIPS VARIABIL IS (BEACH) S. variabilis was the first species oi Sericothrips described in North America (Beach 1896) and is one of the most common in the eastern states. It occurs abundantly on soybeans and other legumes, but its life history and the economic damage it causes are largely unknown. Life-history studies have been mad{ on several economically importani thrips, the most complete being those of Horton (1918) on Scirtofhrips citn (Moulton), Bailey (1933) on Caliothripi fasciatus (Pergande), and Ghabn (1948] on Thrips tabaci (Lindeman). Othei accounts by Bourne (1926), Davidsoi & Bald (1930), Foster & Jones (1915) McKenzie (1935), Rivnay (1935), Rus- sell (1912), Sakimura (1932), Schopj (1936), Watts (1934), and White (1916] are more brief. Bailey (1938) sum- marized and compared the life histories of several thrips of economic impor tance in California. Rearing methods are described by Bailey (1932 anc 1933), Rivnay (1935), and Callan (1947), The following data on S. variabilU are intended to provide information on the development of the immature stages, the effects of temperature and photoperiod, the site of pupation, mating, and predators, and an assess- ment of the economic importance oi the species. METHODS Two types of rearing containers were used. The first was a covered plastic petri dish (35 mm in diameter and 10 mm deep) set vertically in a wooden rack. A soybean leaf was trimmed to fit into the dish with its stem extending through a hole in one side of the dish and into a vial of water below. The second rearing container was a 100- X 15-mm covered glass petri dish August, 1974 Vance: Larvae of the Sericothripini 151 containing two soybean leaves and a piece of filter paper which was moist- ened daily. Larvae and adults were collected from soybeans on the South Farm of the University of Illinois, Urbana. Rearing was done at controlled tem- peratures of 21.0°, 26.5°, and 32.0° C under constant light and at 22.0° C under an 8-hour-per-day light photo- period. Two cultures were confined at each temperature. One culture was started with eggs already present in the leaves. A second culture was started with 10 adults. The number of larvae at each stage of growth was recorded twice daily between 0800 and 0900 hours and between 1600 and 1700 hours. Data were tabulated and analyzed by recording the duration of each im- mature stage and computing each mean. Further analysis included the calculation of the standard error of the mean and t tests at a significance level of 0.01. The site of pupal development was determined by examining for pupating thrips field samples of soil collected from beneath soybean plants at depths of 1 inch (25.4 mm) and at 4-5 inches (101.6-127.0 mm). Soil was placed in the lower end of a glass petri dish held at a 45° angle. Soybean leaves were set upright in the dish with the stems resting on the soil. Larvae pres- ent on the leaves could therefore drop or crawl to the soil when ready to pupate. Sticky traps were set in the field to determine how tlie second-stage larvae reach the ground. Tanglefoot (Tangle- foot Company, Grand Rapids, Michi- gan) was placed in 1-inch (25.4-mm) bands 6 inches (1.52.4 mm) from ground level around and directly on the stems of 12 soybean plants to trap any larvae crawling down the stems. Two 12- x 18-inch (.304.8- x 457.2-mm) cardboard sheets covered with Tanglefoot were placed on the ground beneath the plants at least 6 inches (1.52.4 mm) from the stems to catch any larvae dropping from the leaves. FIRST-INSTAR LARVA The mean duration of the first instar of S. variabilis larvae reared at 22.0° C with an 8-hour light photoperiod per day was 73.49 ± 7.32 hours. The mean body length of the cultured im- matures of this instar varied from 560 ± 80 |iim for the early larva I to 720 ±: 70 iJ.m for die late larva L The early larva I has a narrow, tapering abdomen and a disproportionately large head and legs (Fig. 7a). As feed- ing takes place, the body becomes dis- tended due to increases in the sizes of the internal organs, particularly the fat body (Fig. 7b). Cuticular color changes from white in the early larva I to yellow in the late larva I, and in- gested chlorophyl often gives the body a green color. The setae are short and narrowly fanned, setal pair P7 is lacking, and abdominal segment IX has three or four pairs of setae. ( The setal and segmental numbering system used in this report is shown in Fig. 6.) Priesner (1958) speculated, but Ghabn (1948) had proved, that the male larva I has three pairs of setae on segment IX (two dorsally and one laterally), whereas the female has four pairs of setae on this segment (two dorsally, one later- ally, and one ventrally). The sexes can be determined by these setal arrange- ments. Antennal segment IV is covered with random microtrichia, and segment VII is tapered apicaUy. Soon after hatching, the larva begins feeding, never moving far from the hatching site and often hiding in the angles of the larger veins on the lower leaf surface. The larvae are active and move about quickly when disturbed. In late larvae I the old cuticle becomes light gray. It splits dorsoventrally, the head and thorax are pushed out, and the antennae and legs are pulled free. 152 Illinois Natural History Subntey Bulletin Vol. 31, Art. 5 The exuviae is pushed partly down the abdomen by the hind feet, and the remainder of the abdomen is pulled free by forward pressure exerted on the leaf surface by the feet. About 4 minutes are required for this process. SECOND-INSTAR LARVA The mean duration of the second instar of S. variabilis larvae reared at 22.0° C under an 8-hour light photo- period per day was 91.30 ± 10.44 hours. The mean body lengths of the cultured immatures of this instar varied from 910 dz 60 ;um for the early larva II to 1,030 ± 50 pm for die late larva II. A newly molted larva has a narrow abdomen and thorax and a dispropor- tionately large head and legs (Fig. 7c). As the larva feeds, the abdomen, par- ticularly, and the thorax become dis- tended (Fig. 7d). The cuticular color changes from white in the newly molted larva to orange, often with red hypodermal pigmentation, in the late larva II (although the red pigmentation was not observed in laboratory-reared larvae). Green body coloration due to ingested chlorophyl was predominant in many larvae. The setae are long and widely fanned, appearing proportionately longer in the early larva II because the lengths of the setae remain unchanged throughout the larval stage. Setal pair P7 is present, and abdominal segment IX has five or six pairs of setae. Sex was determined by following Priesner (1958) on the number of setae on segment IX. Those larvae with five pairs of setae (two dorsally, two laterally, and one ven- trally) were presumed to be females, and those with six pairs of setae (two dorsally, two laterally, and two ven- trally) were presumed to be males. Priesner ignored one pair of lateral setae (A3 in this study) because they were greatly reduced, and gave the setal counts as four and five pairs. However, A3 is not reduced in larvae of certain genera (e.g., Aeolothrips, Merothrips, and Hetewthrips), and for the sake of uniformity, this pair of setae was included in all setal counts here. The color of the setae are white immediately following the molt (some- times making newly molted second- stage larvae easily confused with mid- first-stage larvae) but soon become sclerotized and turn brown. Antennal segment IV has microtrichia only on the annulations. Second-instar larvae feed on the leaf surface and occasionally hide in crev- ices. In nature they are almost always found on the undersides of leaves, but they also occur on the upper sides in laboratory cultures. Near the end of the larval stage, the larvae drop to the ground and enter the soil for pupa- tion. PREPUPA The mean duration of the pre- pupal stage of S. variabilis reared at 22.0° C under an 8-hour light photo- period per day was 22.00 ± 2.38 hours. The mean body length was 1,180 ± 80 ^m. Changes in size are - imper- ceptible during the prepupal stage. The color is predominantly orange; wing pads are present, reaching posteriorly to the second abdominal segment; the antennae are indistinctly segmented, protruding anteriorly from the head; and the setae are simple and short. Abdominal segment IX lacks the cuticu- lar spines found in the prepupae of some genera (Fig. 7e). Female prepupae possess two pairs of short lobes arising ventrally on abdomi- nal segments VIII and IX; these are the buds of the ovipositor valves. Male prepupae lack these structures (Priesner 1960). The prepupal period is normally passed in the soil, but in laboratory cultures where soil was unavailable, prepupation readily took place on the leaf surface. Under laboratory rearing conditions, the prepupae were quies- August, 1974 Vance: Larvae of the Sericotheipini 153 cent and nonfeeding and were usually hidden in crevices between the large leaf veins; activity was observed only when the prepupae were disturbed or threatened. PUPA The mean duration of the pupa stage of S. variabilis reared at 22.0" C under an 8-hour light photoperiod per day was 74.00 ± 2.83 hours. The mean body length was 1,040 ± 60 /jui. No change in size was noted during pupal development. The color is predomi- nantly orange during this stage. The wing pads reach the sixth abdominal segment, and the antennae are recurved along the dorsum of the head. The setae are simple and pointed and longer than in the prepupa. Abdominal seg- ment IX lacks the cuticular spines found in the pupae of some genera (Fig. 7f). The ventral lobes on segments VIII and IX in female pupae are longer and better developed than those found in female prepupae. Male pupae have a bluntly triangular production ventrally at the hind margin of segment IX. Pupal development took place in the upper inch (25.4 mm) of soil beneath soybean plants or in the soil provided in laboratory cultures. In cultmes where soil was not available, pupation readily took place on the leaf surface, the quiescent, nonfeeding pupae being hidden between the larger leaf veins. ADULT Adults of S. variabilis may be dis- tinguished from those of other species of the genus in Illinois by the following combination of characteristics (Stan- nard 1968 ) : each fore wing with two sharply defined crossbands; the pronotal blotch completely dark in contrast to the rest of the pronotum and deeply incised medially and posteriorly by yellow; anterior pronotal striations closely spaced; several abdominal seg- ments dark brown. Adults are quite active and, when disturbed, dart about or jump rapidly. Adults seldom survive long in a cul- ture dish when transferred from field samples but remain alive for up to 4 or 5 days when reared in the laboratory. EFFECT OF TEMPERATURE AND PHOTOPERIOD ON DEVELOPMENT Both temperature and photoperiod affected the durations of the immature stages of S. variabilis (Table 1 and Fig. 1). Under constant light the dura- tions of the stages were about 27 per- cent longer than that required at about the same temperature under an 8-hour- per-day light photoperiod. Temperature and durations of tlie stages were in- versely correlated, the most rapid de- 38.0- 154 Illinois Natubal History Survey Bulletin Vol. 31, Art. 5 Table 1 .—Duration of immature stages of Sericothrips variabilis at different temperatures and photoperiods. Tine numbers of insects observed are in parentheses. Temperature (in Celsius) and Photoperiod August, 1974 V.\NCE: Lakvae of the Sericothripini 155 time lapse to this point from the initial mounting was 22 seconds. Two seconds after making genital contact, the male dismounted while maintaining genital contact, and both male and female remained motionless for 51 seconds fac- ing in opposite directions. Contact was then broken, and each went in a sep- arate direction. PREDATORS Three predators were found in as- sociation with S. variabilis in the lab- oratory cultures: Aeolothrips fasciatus (Linneaus) (Thysanoptera: Aeolo- thripidae), Oritis in.sidiosus (Say) (Heteroptera: Anthocoridae), and mites of the family Phytoseiidae ( Acarina ) . Several A. fasciatus immatures ap- peared in the cultures and developed along with S. variabilis. The Aeolo- thrips larvae were observed feeding on Sericothrips larvae on three occasions. One Aeolothrips reached maturity in the culture dish, as did others reported on by Robinson, Stannard, & Armbrust (1972). Phytoseiid mites were observed carry- ing dead Sericothrips larvae on two oc- casions but were not observed actually feeding. According to Chant ( 1958 ) and Chant & Fleschner (1960), phyto- seiid mites can be important predators of certain phytophagous mites, but little is known of their predation on thrips or other insects. In laboratory cultures these mites survived well and could be reared easily with thrips for study on the interaction between the two. Nymphs of O. insidiosus were ob- served in association with S. variabilis on many samples brought from the field and were found several times in the laboratory cultures. Although no preda- tion was observed, it is probable that these anthocorids were feeding on thrips larvae. Borror & DeLong (1964) reported O. insidiosus as predatory on various species of thrips and other in- sects, and Bailey ( 19.33 ) showed that another species, O. tristicolor White, is a predator of the bean thrips, Calio- thrips fasciatus. The adults of tristi- color were observed to consume about one larva an hour, the nymphs appear- ing even more voracious. Both nymphs and adults preferred young larvae. O. indicus ( Renter ) feeds extensively on Taeniothrips nigricornis (Schmutz) (= T. distalis Kamy ) in India ( Raja- sekhara & Chatterji 1970). Other predators reported by Bailey (1933) were larvae of Chrysopa cali- fornica (Coquillett), Hippodamia con- vergens (Guerin), Aeolothrips kuwanai (Moulton), and A. fasciatus. ECONOMIC ASSESSMENT Although S. variabilis is generally considered to be of minor economic importance, Bailey ( 1940 ) rated it as ninth in economic importance among thrips species of the conterminous United States. In laboratory cultures immature stages of S. variabilis apparently caused little damage to soybean leaves, even with a population of 8-10 thrips per leaf, despite the small amount of yel- lowing which was evident at times. During the latter part of the summer, many upper lea\'es on soybean plants in the field showed yellowing, browning, and other evidence of insect-feeding damage. This damage, however, can- not be directly attributed to thrips be- cause a variety of other insects also feed on soybeans. Furthermore, the population levels of S. variabilis in the field were estimated at an average of one or fewer thrips per leaflet at each observation. At this density level little economic damage results. However, thrips damage at levels of 30-60 insects per plant (number per leaflet not stated) was reported in Maryland in July 1971 in the Cooperative Economic Insect Report (U.S. Department of Agriculture 1971). So far as is known. 156 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 S. variabilis does not transmit plant viruses. Other Sericothripini of economic im- portance include the citrus thrips, Scirtothrips citii, ranked seventh among economic thrips species by Bailey ( 1940 ) ; the grape thrips, Drepano- thrips reuteri Priesner, given a rating of 11 and considered of minor impor- tance; the long-vi'inged thrips, Scirto- thrips longipennis (Bagnall), ranked number 20 and considered as rarely of importance; and Echinothrips ameri- canus Morgan, ranked 31 and also con- sidered rarely of economic importance. PHYLOGENY Interpretations of the phylogeny of the Sericothripini and the relationships of that tribe to some of the other groups in the Thysanoptera were made on the basis of larval characteristics, as pre- sented here. Larval characters used in assessing the relationships of the major groups of Thysanoptera were: (1) the degree of elongation of antennal segments III and IV, (2) the length of antennal segment V, ( 3 ) the presence or absence of antennal microtrichia, (4) the pres- ence or absence of antennal annula- tions, (5) the tendency toward fusion of antennal segments, (6) the degree of ornateness of the setae, ( 7 ) cuticular sculpturing, (8) the presence or absence of cuticular sclerotization, (9) the pig- mentation of the cuticle, ( 10 ) general body size, (11) the modification of setae into spines on abdominal segment IX, and (12) the presence or absence of a posterior comb on abdominal seg- ment IX. The characters used in assessing the phylogeny of the Sericothripini were: ( 1 ) the distinctness of the suture be- tween antennal segments IV and V, ( 2 ) the density of microtrichia on antennal segment IV in larva I, (3) body size, (4) the amount of cuticular pigmenta- tion, (5) the presence or absence of hypodermal pigmentation, (6) the pres- ence or absence of brown sclerotized body areas, (7) setal length, (8) the degree of setal ornateness, (9) the presence or absence and the position of setae, (10) the presence or ab- sence of setal basal rings, (11) the density of the cuticular microtrichia, and ( 12 ) the presence or absence of cuticular pustules. In selecting these characters and in determining their primitive and derived states, it was assumed that: ( 1 ) charac- ters found mainly in primitive groups are primitive, and (2) characters re- garded as primitive in adult Thysanop- tera (Stannard 1968; Gentile & Bailey 1968 ) might be supposed, with reserva- tions, to be primitive in the larval stages also. Large body size, mod- erately ornate and long antennal seg- ments, greater degrees of coloration, moderately ornate setae, the presence of cuticular microtrichia, lack of body pustules, lack of a posterior comb on abdominal tergite IX, and setae modi- fied into spines on the terminal abdomi- nal segments were considered to be primitive features of the Sericothripini and of some other tribes of the Thripidae. Each of the characters was assigned a value from to 2 for each Illinois genus of the Terebrantia and for each species of the Sericothripini found in Illinois. A value of indicates a plesio- moi-ph or primitive condition for the character in the group or species; a value of 1, an intermediate or variable condition; and a value of 2, the apomorph or derived condition. The character states and values are sum- marized in Tables 2 and 4, and scores and sums are summarized for 29 genera and one family in Table 3 and for 16 species of the Sericothripini in Table 5. The sum of the values for the 12 characters gives a measure of the de- gree of divergence of the taxon from the primitive, ancestral stock. These values are shown graphically in Fig. August, 1974 Vance: Larvae of the Sericothripini 157 2 and 4, and the inferred phylogenies are represented in Fig. 3 and 5. PHYLOGENY OF THE THYSANOPTERA The Aeolothripidae ha\'e generally been accepted as representing the most primitive group because of their simi- larities to the more primiti\'e Cor- rodentia ( Psocoptera ) ( Stannard 1957 ) . According to Stannard (196S), the Merothripidae and Heterothripidae arc of more recent origin, and the Thripidae the most recent of the Terebrantian families. The Tubulifera, according to Stannard, e\olved from a phyletic line related to the Heliothripinae of the Thripidae, the evidence being the many sunilarities between certain members of the two groups and the many spe- cialized features of the Tubulifera. Gen- tile & Baile)' ( 1968), howexer, bclie%ed that the Merothripidae and Thripidae evolved from the Heterothripidae, and Priesner ( 1926Zj-1928) felt that the Merothripidae represented a possible link between the Terebrantia and the TubuUfera because of certain inter- mediate features found in merothripids. The phylogenetic and systematic status of the tribes in the family Thripidae have been much debated because of the difficulty in delimiting groups at this level. Stannard (1968) recognized the Sericothripini, Dendro- thripini, and Thripini but did not sep- arate the Chirothripini and Anapho- thripini because they were difficult to categorize. Gentile & Baile\' (1968) suggested a phylogenetic sequence for the tribes, from most primiti\e to most advanced: Heliothripini, Anaphothrip- ini, Chirothripini, Sericothripini, Den- drothripini, and Thripini. These au- thors indicated that the Thripini have become specialized by degeneracy. All of these phylogenetic arrangements were derixed, primarily, from studies of adult characteristics. An interpretation of the higher Thy- sanoptera phylogeny, based on larval characters, can be depicted as in Fig. 3. Most larval features in aeolothripids were assumed to be primitive although lack of color and pigmentation seemed to be an advanced trait. This family is characterized by such primitive larval features as spines (modified Al and A2 setae) on abdominal tergite IX; large body size; cuticular sculpturing lacking pustules; complete anterior and pos- terior tentorial arms (personal com- munication, B. S. Heming, 31 January 1972); antennal segments III-V elon- gate and segments II-VII strongly an- nulated, with prominent microtrichia. From the Aeolothripidae two phyletic lines seem to have emerged: the mero- thripid-phlaeothripid (Tubulifera) Une and the heterothripid-thripid line. The merothripid line is characterized by the retention of a smooth cuticle; long fifth antennal segment; large body size; the loss of antemial annulations and microtrichia; complete anterior and posterior tentorial arms (personal com- munication, B. S. Heming, 31 January 1972); and a tendency toward the fusion of antennal segments VI and \^I. The heterothripid line is charac- terized by the retention of antennal annulations and microtrichia; the de- \elopment of cuticular pustules; small bod)' size; the reduction of the fifth antennal segment; and, occasionally, the fusion of antennal segments VI and VII. The merothripids are more special- ized than are the Aeolodiripidae in the elongation of antennal segments III-V ( V remaining equal to IV ) , the reduc- tion of antennal annulations, the loss of annular microtrichia, the fusion of antennal segments VI and VII, and a partial reduction of the spines on ab- dominal tergite IX. Merothripids re- tain such aeolothripid features as ab- dominal spines, simple setae, smooth cuticle, large body size, and antennal segment V unreduced and equal to seg- ment IV. 158 Illinois Natxiral History SLm\'EY Bulletin Vol. 31, Art. 5 Table 2.—Phylogenetically significant characters of the Thysanoptera and their charac- ter states and values. Character Number and State Value" I Antennal segments elongated Autennal segments not elongated 2 II Antennal segment V long Antennal segment V reduced 2 III Antennal segments with prominent microtrichla Antennal segments with microtrichla reduced 2 IV Antennal segments with prominent annulations Antennal segments with annulations reduced 2 V No fusion of antennal segments Fusion of certain antennal segments 2 VI Setae ornate or long Setae simple or short 2 VII Cuticle without pustules Cuticle with pustules 2 VIII Brown sclerotized body areas present Brown sclerotized body areas lacking 2 IX Prominent cuticular and hypodermal coloration Little cuticular and hypodermal coloration 2 X Body large Body small 2 XI Setae on terminal abdominal segments modified into spines Setae on terminal abdominal segments not modified into spines 2 XII Posterior comb lacking on abdominal segment IX Posterior comb present on abdominal segment IX 2 An intermediate or variable state was given a value of 1. The Tubulifera are more specialized viously intermediate in the Hetero- than the Merothripidae in the total thripidae is the length of antennal seg- loss of antennal annulations and of ment V; in aeolothripids it is equal to abdominal spines on tergite IX, but the the length of segment IV, and in two groups are similar in the retention thripids it is reduced to less than one- of a smooth cuticle, large body size, fourth the length of segment IV. In a long fifth antennal segment, and oc- the heterothripids, however, antennal casional fusion of antennal segments segment V is about one-half the length VI and VII. of segment IV. Just as the merothripids are pos- The Thripidae have retained antennal sibly intermediate between the Aeolo- annulations and microtrichla, but the thripidae and the Phlaeothripidae, so length of antennal segment V has been the heterothripids may be intennediate greatly reduced, body size has become between the Aeolothripidae and the smaller, and cuticular pustules have Thripidae. The heterothripids retain appeared. Many features vary from a such aeolothripid features as annula- primitive to an advanced state within tions on antennal segments II-VII and the group. prominent spines on abdominal seg- The family Thripidae shows con- ment IX but also have characteristic siderable specialization and diversifica- thripid features, such as reduced third tion. As the Tubulifera became spe- and fourth antennal segments, the re- cialized into a fungus-eating niche, the tention of antennal annulations and Thripidae diversified into a phytopha- microtrichia, the reduction of the ten- gous niche and tended toward an evolu- torium, and the development of cuticu- tionary degeneration or simplification of lar pustules. One feature that is ob- many characters. Since the Thripidae August, 1974 160 Illinois Natur.\l History Sltrvey Bulletin Vol. 31, Art. 5 nulations, whereas in other groups they occur mainly on the annulations and only sparsely between them. The most primitive subfamily in the Thripidae is the HeUothripinae. This subfamily shares with the Heterothripi- dae the retention of annulations on antennal segments V-VII, less reduc- tion of segment V than occurs in most thripids, an elongation of segment VII, and, in some genera, an elongation of segments III and IV ( this latter feature / / V August, 1974 Vance: Labvae of the Sericothripini 161 reapproaching that in the Aeolothripi- dae). The Hehothriphiae share with the Thripinae a partial reduction of an- tennal segment V and the loss of spines on abdominal tergite IX. The Heliothripinae ha\'e such primi- tive thripid features as large pustules, brown sclerotized body areas in many species, long anal setae, and a great diversity in ornamentation. The tribe Chirothripini shares several primitive features with the HeUo- thripinae. The genus Limotlirips, like the Heliothripinae, has a reduction in the number of annular microtrichia and brown sclerotized body areas. Segment V in the antennae of first-stage larvae of Limothrips is elongate and has two annulations, a feature found only in more primitive groups, including the %8-L\. g^e INIdlMHi s-a; ° iNidiaHioaaN3c %9'6 INIdiaHi03IM3S %l'S INIdldHiOHdVNV 3VNIdiaHiOn3H avaidiMHioasiSH (Vd3dnngni) %r6t7 3V0IdIdHiO3VlHd 3VaidIMHiOM3W 3VOIdIdHJ,0103V 162 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 Table 4.—Phylogenetically significant characters of the Sericothripini and their character states and values. Character Number and State Value" I Antennal segment V distinct in larva I Antenna! segment V partially fused to segment IV in larva I 2 II Microtrichia densely placed on antennal segment IV Microtrichia sparse on segment IV 2 III Large body Small body 2 IV Cuticle darkly pigmented Cuticle lightly pigmented 2 V Hypodermal pigment present Hypodermal pigment absent 2 VI Brown sclerotized body areas present Brown sclerotized body areas not present 2 VII Setae long Setae short 2 VIII Setae ornate Setae not ornate (simple) 2 IX Some setae reduced or lacking All setae normally present 2 X Setal basal rings present Setal basal rings absent 2 XI Microtrichia dense on cuticle Microtrichia sparse on cuticle 2 XII Cuticle with pustules Cuticle without pustules 2 * An intermediate or variable state was given a value of 1. Heliothripinae. The second-stage an- certain setae on the terminal abdominal tennae of Limothrips are typical of segments into setaelike spines, a con- those of the Thripinae. dition found only in the primitive fami- Within the Chirothripini, Limothrips, 'i^^- with normal antennae, long knobbed The Anaphothripini have antennal setae, and brown sclerotized body areas, segment V reduced in the first-stage is most primitive. Chirothrips exhibits larva, and have shorter antennal seg- an extreme evolutionary degeneracy ments, less ornate setae, shorter anal and specialization. Some Chirothrips setae, and less diversification than have larvae, at least, spend their whole ex- the Heliothripinae. istence within a grass floret (Watts The tribe Sericothripini is transi- 1965); the antennae and legs of the tional between the more primitive and larvae are greatly reduced, the setae the more specialized tribes in the are minute and pointed, and little Thripidae. The Sericothripina share, brown sclerotization is present. in some species, several characteristics Tlie Anaphothripini also share many with the Anaphothripini, and the Scirto- primitive traits with the Heliothripinae. thripina with the Dendrothripini. The Cuticular pustulation and the lack of annulipes group of Sericothrips have microtrichia are very similar between such seemingly primitive features as the two groups, and many Anapho- brown sclerotized body areas, hypo- thripini have brown sclerotized body dermal pigmentation, large basal rings areas similar to those in the Helio- on the setae, and in Sericothrips cingu- thripinae. Genera such as Oxythrips kitus small cuticular pustules. Except and Chilothrips show a modification of for cuticular pustules these features are August, 1974 164 Illinois Natural History Survey Bxjlletin Vol. 31, Art. 5 setae in Scirtothrips are short and pointed, and cuticular pustules are totally lacking, these two features con- sidered here to be derived. The Scirtothrips species show a pat- tern of setal simplification. S. nivetis has four pairs of setae terminally fun- neled, and S. taxodii and S. brevipennis have only two pairs of funneled setae, the latter situation being the derived state. In the Sericothripina the genus Seri- cothrips contains two subgroups, the anmiUpes and tiJiae groups. The tiJiae group is characterized by light body coloration, a lack of hypodermal pig- mentation, reduced brovini sclerotized areas, and reduced rings at the bases of the setae, all considered here to be derived conditions (Fig. 5). The annulipes group is characterized by the presence of cuticular and hypodermal / I. « • o< s3mvA a3iovavHD do ivioi E-- o-a (U o S L U U 3 d L A »u q August, 1974 Vance: Labvae of the Sericothripini 165 pigmentation, brown sclerotized body areas, occasional enlarged rings at the setal bases, and, in one species, by small cuticular pustules, all suggested here to be the primitive state. The tiliae group includes campestris, heachae, samhuci, tiliae, niibiUpennis, baptisiae, and langei (Fig. 5). The first five species all have long body setae, and the other two, short setae. S. campestris resembles members of tlie annuJipes group, having orange cuticu- lar pigmentation and generally long, wide body setae. For these reasons campestris is considered the most primi- tive of the tHiae group. S. heachae, S. siuuad LA3jq TsBuTT aeis ladeq - siuuaditiqnu • BE L [ n ' s U}S3diije3 • 5 4-'" S9d L [PUUC ' sniB [n5u p . snueoijsuic' 166 Illinois Natural History Surx'ey Bulletin Vol. 31, Art. 5 samhuci, S. tiliae, and S. nubilipennis are light colored and have long setae: beachae and samhuci have wide setae, and tiliae and nubilipennis narrow setae. The larvae of the latter two species are seemingly indistinguishable, suggesting that they separated rela- tively recently. S. baptisiae and langei are considered to be the most derived of the tiliae group because of their setal reduction, those of langei being so narrow as to approach the condition found in the Scirtothripina. The annulipes group includes cingu- latus, annulipes, pulchellus, and pos- sibly variabilis (Fig. 5). The most primitive species is cingulatus, as evi- denced by its brown body areas, the presence of small cuticular pustules similar to those of the Chirothripini, its pteronotal sclerotized plates, and its enlarged setal basal rings. S. annulipes and pulchellus have a reduced amount of brown coloration and fewer pustules, but possess pteronotal sclerotized plates, setal basal rings, and hypodermal pig- mentation. S. variabilis lacks pteronotal sclerotized plates, but has hypodermal pigmentation and somewhat enlarged setal basal rings. The evolutionary status of the Echi- nothripina is uncertain. Echinothrips species have large body size and ornate setae, both primitive features, but also show derived features, such as weak body coloration and sclerotization and a reduction in certain setae. SYSTEMATICS The known larvae of the Thysanop- tera of Illinois are described here at the family level and for the suborder Terebrantia at the subfamily and tribal levels. Genera and species larvae are described only for the tribe Serico- thripini. Larval descriptions pertain to the second-instar larva unless otherwise stated and include as little repetition as possible from higher to lower groups. A key is included to the major groups and to many genera of the Illinois thrips fauna, and keys to the species of some genera of the Sericothripini are given. Measurements, taken with a cali- brated ocular micrometer, are ex- pressed in microns. They include lengths and widths of antennal seg- ments, antennal length, body length (excluding antennae), head and prono- tal length and width, and lengths of certain body setae, the particular setae measured depending on the genus con- sidered. The setal numbering system used in this report is given in Fig. 6. KEY TO IMMATURES OF THE THYSANOPTERA 1. Antennae projecting forward, with distinct segmentation; wing pads absent (LARVA) 5 Antennae short, projecting back over head or to side of head and indis- tinctly segmented; if antennae pro- ject forward, they are indistinctly segmented 2 2. Antennae directed forward and in- distinctly segmented or short and directed laterally or directed poste- riorly along sides of head, not reach- ing anterior margin of prothorax ( If antennae are recurved over head, wing pads reach only to second or third abdominal segment.) (PRE- PUPA) 3 Antennae are recurved posteriorly over dorsum of head or along sides of head, reaching or surpassing an- terior margin of pronotum (PUPA) 4 3. Antennae long and directed forward (recurved over head in Aeolo- thrips) ; wing pads, if present, ex- tending posteriorly only to second or third abdominal segment; ab- dominal segment X not tubelike Terebrantia Prepupa Antennae short and directed to side or if long, posteriorly directed along sides of head; wing pads absent; abdominal segment X tubelike or elongately conical. .Tubulifera Prepupa 4. Antennae directed posteriorly over dorsum of head; wing pads, if pres- ent, reaching abdominal segment VI or VII; abdominal segment X never tubelike Terebrantia Pupa Antennae directed posteriorly along sides of head; wing pads, if pres- ent, reaching to abdominal segment August, 1974 Vance: Larvae of the Sericothripini 167 II or III; abdominal segment X GENERIC KEY TO LARVAE tubelike or elongately conical OF THE TEREBRANTIA OF ILLINOIS Tubulifera Pupa i Prothorax usually with six pairs ot 5. Abdominal segment X never tube- setae; abdominal segment IX with like, usually broader than long; mid- three or four pairs of setae. .. Larva I die antennal segments with micro- Prothorax usually with seven pairs of trichia-hearing annulations setae; abdominal segment IX with Terebrantia Larva five or six pairs of setae (LARVA Abdominal segment X tubelike or II' ^ elongately conical, usually longer 2. Antennal segment V from one-half than wide; middle antennal seg- to equal to the length of antennal ments without annulations (Fig. 21, segment IV (PRIMITIVE FAMI- 42, and 61) Tubulifera Larva LIES) 3 Fig. 6.—The external morphology of a Terebrantian larva (Sericot-nrips !a..sei(. 168 Illinois Natural History Sxton^ey Bulletin Vol. 31, Art. 5 Antennal segment V much less than one-half the length of segment IV (usually about one-fifth as long) (THRIPIDAE) 6 3. Antennal segment V one-half the length of segment IV (Fig. 22) ; seg- ments VI and VII with visible an- nulations Heterothripidae (genus Heferothrips ) Antennal segment V equal or subequal to length of segment IV; segments V, VI, and VII with or without an- nular rings 4 4. Antennal segments VI and VII fused; segments V-VII without an- nular rings, and segments III and IV not greatly elongated (Fig. 20) Merothripidae ( genus Merothrips ) Antennal segments VI and VII not fused; segments V-VII with annu- lations, and segments III and IV elongated (Fig. 18) (AEOLOTHRIP- IDAE ) 5 5. Four median dorsal setae on ab- dominal segment IX thornlike (Fig. 57) Aeolothrips Four posterior setae on abdominal segment IX not thornlike; not yet found in Illinois Franklinothrips 6. Antennal segment VII greatly elon- gated, length seven to eight times the greatest width (Fig. 25) (HB- LIOTHRIPINAE) 7 Antennal segment VII not greatly elongated, length only two to three times the greatest width (THRIP- INAE) 10 7. Abdominal segment X with six anal setae 8 Abdominal segment X with less than six anal setae 9 8. Body setae somewhat fanned for entire length (Fig. 46) . . . .Caliothrips Body setae moderately long and sim- ple, with hyaline terminal knob (Fig. 43) Heliothrips 9. Body setae moderately long and widely tunneled at tip. .Parthenothrips Body setae very short and simple (Fig. 65) Hercinothrips to. Body cuticle generally smooth, with minute pustules or a stippling of fine microtrichia; abdominal seg- ment IX never with a posterior comb (CHIROTHRIPINI, SERICO- THRIPINI, DENDROTHRIPINI) ... 11 Body cuticle generally with raised pro- tuberances or pustules, with or without microtrichia; with or with- out a posterior comb on abdominal segment IX (ANAPHOTHRIPINI, THRIPINI) 19 11. All major dorsal body setae ex- panded and fimbriate or quite long and fimbriate, or if most dorsal body setae are small and simple, cuticle densely covered with fine but obvious (under high-power mag- nification) microtrichia (SERICO- THRIPINI) 12 Setae mostly small and simple and cuticle with stippling pattern devoid of obvious microtrichia (DENDRO- THRIPINI, CHIROTHRIPINI) 15 12. Setae only terminally tunneled, not greatly fimbriate (SCIRTOTHRIP- INA) 13 Setae fanned and fimbriate for most of length (except in Sericothrii)s langei) (SERICOTHRIPINA) 14 Setae long, unexpanded, and fimbriate for most of length (Fig. 54) (ECHI- NOTHRIPINA) Echinothrips 13. Cuticle with closely set microtri- chia; a maximum of four or five pairs of setae expanded, the re- mainder small and simple (Fig. 49 and 50) Scirtothrips Cuticle with prominent stippling and with less dense and less obvious microtrichia; all major dorsal body setae terminally tunneled (Fig. 52) Drepanothrips 14. Associated adults with eight anten- nal segments; found statewide in Illinois Sericothrips Associated adults with seven antennal segments; found only in Volo Bog in Lake County, Illinois. .. .Zonothrips 15. Eye facets large and eyes bulging at sides of head; brown sclerotized body areas lacking (DENDRO- THRIPINI) 16 Eye facets reduced and eyes not bulg- ing at sides of head; brown sclero- tized areas present or if absent, antennae and legs greatly reduced (CHIROTHRIPINI) 18 16. Lateral abdominal setae with mi- nute terminal knobs Leucothrips Certain dorsal body setae terminally tunneled 17 17. Lateral setae expanded only on ab- dominal segment IX (Fig. 71) .... Dendrothrips Lateral setae expanded on abdominal segments II-IX and posteroangular August, 1974 Vance: Larvae of the Sericothripini 169 setae also expanded (Fig. 74) .... Pseudodendrothrips S. Antennae and legs greatly reduced; all body setae reduced and pointed (Fig. 45) Chirothrips Antennae and legs not reduced; cer- tain body setae on posterior abdom- inal segments long and knobbed (Fig. 44) Limothrips !). Cuticular protuberances without mi- crotrichia; abdominal segment IX without posterior comb (except in some Atuipliothrips) ; body often with brown sclerotized areas; all or certain setae often knobbed or blunted (ANAPHOTHRIPINI) .... 20 Cuticular protuberances with or with- out microtrichia; abdominal seg- ment IX with a posterior comb (ex- cept in Scolothrips) ; body without brown sclerotized areas; setae usu- ally pointed (THRIPINI) 24 0. Median and lateral dorsal setae on abdominal segment IX all nearly equal in length and width 21 Median setae significantly shorter or thicker than lateral dorsal setae on abdominal segment IX 22 1. Dorsal setae on abdominal segment IX pointed, with prominent rings at bases (Fig. 67) Anaphothrips Dorsal setae narrowly tanned, with- out fimbriation and without basal rings Chaetanaphothrips 2. Most body setae roundly blunt; mid- dorsal setae of abdominal segment IX shorter and much thicker than lateral setae and almost thornlike (Fig. 66) 23 All body setae pointed; mid-dorsal setae of abdominal segment IX not thornlike; lateral setae long and whiplike Aptinothrips 3. Abdominal tergal sculpture in form of wavy, thickened, raised, trans- verse striae Chilothrips Abdominal tergal sculpture in form of raised pustules arranged in trans- verse rows Oxythrips 4. All body setae quite long (each epimeral seta= 60,nm); posterior comb absent on abdominal segment IX (Fig. 56 and 77) Scolothrips Body setae much shorter, normally less than 30-40 ^m; posterior comb present on abdominal segment IX. . 25 ;5. Antennal segment IV reduced and shorter than the combined length of segments V-VIl (IV about two- thirds the length of V-VIl) (Fig. 37) Ctenothrips Antennal segment IV not reduced and equal to or longer than the com- bined length of segments V-VII. ... 26 26. Other Thripini genera (.Baliothrips, Dorcdilothrips, FrankUnieUa, Irido- thriiis. Mirroccijhalothiip.s, Odonto- thrip.s, Plesiotlirips, Bhaphidothrips, Taeniothrips, and Thrips) larvae cannot be keyed at this time. AEOLOTHRIPIDAE Uzel (1895) Larva.—Antennae (Fig. 8, 18, and 19) each seven segmented; segments III-V elongate, III-VII with well- developed, numerous annular rings; microtrichia present on most annuli. Antennal segment V as long as or longer Uian IV. Sense cones ( segments IV-VI) generally long and pointed. Head ( Fig. .39 ) usually rounded from the dorsal aspect, with well-de\eloped tentorium, mouth cone short and hy- pognathous; body elongate and cylin- drical. Setae usually long, moderately stout, and pointed or knobbed. Ab- dominal tcrgite IX ( Fig. .57 ) with two median pairs of setae modified into stout spines (not modified in Frank- Unothrips). Cuticle with fine micro- trichia producing a stippled pattern. Larva I lacking stout spines on ab- dominal segment IX. Diagnosis.—Larvae of the Aeolo- thripidae are easily distinguished by antennal features: segments Ill-V are elongate, annular rings are numerous on segments III-VII, and segment V is as long as or longer than segment IV. In heterothripids, antennal seg- ment V is about one-half the length of segment IV, and in the Thripidae, seg- ment V is greatly reduced and less than one-fourth the length of IV. In the Merothripidae, antennal seg- ment V is as long as IV, but both are relatively short, fewer annulations oc- cur on the antennal segments, and seg- ments VI and VII in Merotluips are fused. 170 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 Descriptions of Aeolothrips, Mehn- thrips, and Atikothrips larvae and a key to species of Aeolothrips larvae were given by Priesner (1926^-1928). In 1960 Priesner presented a key to the genera of larval Aeolothripidae, includ- ing Fianklinotlirips and Rliaphidotlirips in addition to those mentioned above, and gave descriptions of the larvae of Melantlirips and Rhaphidothrips and some larval characters of Aeolothrips and Franklinothrips. Fig. 7.— Immature stages of Sericothrips variabilis, a, Early first-instar larva, b, Late first-instar larva, c, Early second-instar larva, d. Late second-instar larva, e, Prepupa. f. Pupa. August, 1974 Vance: Laevae of the Sebicothkipini 171 Melis ( 1959 ) published descriptions (in Italian) and illustrations of Aeolo- thrips and Melantlirips immatures. Material Examined.—INHS: AeoJo- thrips hicolor Hinds; 1 larva I; June; on grasses; Vermilion County, Illinois. A. fasciattis (Linneaus); 5 larvae I, 2 larvae II; August and September; on soybeans; Champaign County, Illinois. A. vittipennis Hood; 3 larvae I, 3 lar- vae II; June and July; on black locust; Johnson and Union counties, Illinois. MEROTHRIPIDAE Hood (1914) Larva.—Antennae (Fig. 20) each six segmented, segments VI and VII usu- ally fused; segments not elongate, ha\'- ing faint annular rings and lacking microtrichia; segment V as long as segment IV. Head and pronotum (Fig. 40) small and tapering anteriorly, posterior and anterior tentorial anns joined. Body cylindrical. Setae generally long and pointed. Abdominal tergite IX ( Fig. 58) with two median pairs of setae modified into stout spines. Cuticle with very fine microtrichia on abdomen and pteronotum, producing a stippled pattern. Diagnosis.—Merothripid larvae can be easily distinguished by the fusion of antennal segments VI and VII and by the reduction of annular rings and absence of the annular microtrichia found in other families of the Tere- brantia. The larvae of the Merothripidae ap- pear to be transitional between those of the Aeolothripidae and Phlaeothripi- dae (suborder Tubulifera). Antennal segment V is relatively long in Mero- thrips, as in the Aeolothripidae and Phlaeothripidae, but it is reduced in the Heterothripidae and Thripidae. Mero- thripids have the median setae of ab- dominal tergite IX modified into spines, as in the Aeolothripidae, and a reduced number of annular rings and a lack of microtrichia on the antennal segmc-nts, as in the Phlaeothripidae. Material Examined.—INHS: Mero- thiips morgani Hood; larva II, 1 $ ; 28 September 1952; on ground cover; Key West, Florida. HETEROTHRIPIDAE Bagnall (1912) Larva.—Antennae (Fig. 9 and 22) each seven segmented, segments II-V with four or five annular rings, seg- ments VI and VII with two or three annular rings; microtrichia present on most rings; segment V about half the length of IV. Setae short to long and blunt to terminally funneled. Abdominal tergite IX (Fig. 59) with two median pairs of setae modified into stout spines. Cuticle with prominent pustules bear- ing fine microtrichia (Fig. 41). Lar\'a I with stout spines on abdomi- nal segment IX. Diagnosis.—Larvae of the Illinois Heterothripidae can be distinguished by the length of antennal segment V and by a combination of many features which they share with aeolothripid and thripid larvae. Heterothripid larvae ap- pear transitional between Aeolothripi- dae and Thripidae laryae. Antennal segment V is relatively long, annular rings are present on segments VI and VII, and two pairs of setae on abdomi- nal tergite IX are modified into stout spines, characteristics also present in aeolothripids. The shorter antennal seg- ments with fewer annular rings and the presence of cuticular pustules are thripid characteristics. Material Examined.—INHS: Hetero- tliiips arisaemae Hood; 2 larvae I, 10 larvae II; May-June; on jack-in-the- pulpit (Arisaema sp.); La Salle and Carroll counties, Illinois, and Raleigh, North Carolina. THRIPIDAE Stephens (1829) Larva.—Antennae each seven seg- mented, usually only segments III and IV have annular rings (also segments V-VII in the Heliothripinae); micro- 172 Illinois Natural History Surx'Ey Bulletin Vol. 31, Art. 5 tiichia often but not always present on than one-fourth the length of segment annulations; segment V reduced to less IV. 12 Fig. 8-17.—Right antenna (except where indicated) of the first-instar larva. 8. — Aeoloi-hrips vittipennis. 9.—Heterothrips arisaemae. 1 0.—Heliothrips haemorrhoidalis. 1 1 . — Limothrips denticornis. 12.—Anaphothrips secticornis. 13.—Dendrothrips ornatus. 14. — Sericothrips variabilis. 15.—Scirtothrips taxodii. 16.—Echinothrips americanus, left antenna. 1 7. — Frankliniella tritici. August, 1974 Vance: Larvae of the Sericothbipini 173 Abdominal tergite IX without spines (a posterior comb usually present on tergite IX in the Thripini). Setal features and cuticular sculpturing vari- able. Diagnosis.—Lanae of the Thripidae can be recognized by the great re- duction of antennal segment V and by the lack of spines on abdominal tergite IX. The Thripidae include the sub- families Heliothripinae and Thripinae. These subfamilies and their tribes are distinguished by antennal features, cuticular sculpturing, and other charac- teristics. Subfamily HELIOTHRIPINAE Kamy (1921) Larva.—Terminal antennal segment greatly elongate (length seven to eight times the greatest width, as in Fig. 10, 25, 26, and 27 ) ; antennae with annula- tions on segments V-VII, annulations often with no or few microtrichia; sense cones fairly short. Body often with prominent areas of brown coloration. Cuticle usually with small to large pustules, which generally lack micro- trichia. Head usually constricted be- hind the eyes (Fig. 4.3 and 46). Ab- dominal segment IX (Fig. 60, 63, and 65) lacks a posterior comb; segment X sometimes with long anal setae. Body setae variable, often ornate. Diagnosis.—Larvae of the Helio- thripinae are easily recognized by the elongate tenninal antennal segments and by the combination of features mentioned above. The Heliothripinae may be considered the most primitive .subfamily in the Thripidae. Primitive features are the elongate antennal seg- ments, the presence of annulations on the terminal segments, and the shorter sense cones found also in the Aeolo- thripidae. The Heliothripinae resemble the Anaphothripini in ha\'ing cuticular pustulation, cheek constrictions, and body areas of brown sclerotization. They resemble the Chirothripini in ha\'ing a reduced number of annular microtrichia, an enlarged antennal seg- ment V (in the first-stage larva of Limothrips) , and body areas of brown sclerotization. The only native genus of this sub- family in Illinois is CaliotJirips; exotic genera occurring in greenhouses and homes are Heliothrips, Forthenothrips, and Hercinothrips. Material Examined.—INHS: Calio- thiips indicus (Bagnall); 2 larvae I, 1 larva II; 3 March 1970; reared from soybeans; Jabalpur, M.P., India. Heliothrips haemorrhoidalis var. an- gttstior Priesner; 1 larva I, 3 larvae II, prepupa (on slide with 9 lectotype); on plants of virgin forest; Paramaribo, Surinam, S.A. Hercinothrips femoralis (Reuter); 1 larva II; .30 April 19.53; on African violet; St. Louis, Missouri. Parthenothrips dracaenae (Heeger); 1 larva II; March 1952; on Cordyline feminalis leaves; Wahiawa, Oahu, Hawaii. Subfamily THRIPINAE Stephens (1829) Larva.—Terminal antennal segments not greatly elongated (length only two to three times the greatest width), antennae without annulations on seg- ments V-VII, antennal microtrichia and sense cones variable. Body coloration, cuticular sculptiuing, head shape, and abdominal segment IX variable. Ab- dominal segment X lacks long anal setae. Diagnosis.—Lan'ae of the subfamily Thripinae can be distinguished from those of the HeUothripinae by the short, terminal antennal segments and by other featiues not usually occurring in the Heliothripinae. Priesner ( 1957 ) recognized the tribes Dendrothripini, Sericothripini, Tliripini, and Chirothripini in the Thripinae, and included the Anaphothripini under the Thripini as a subtribe. Stannard ( 1968 ) recognized these tribes, too, but tenta- 174 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 Fig. 18-27.—Right antenna of the second-instar larva. 18. — Aeolothrips vittipennis. 19.—Franklinothrips sp. 20.—Merothrips morgani. 21. — Phlaeothripid (Tubulifera). 22. — Heterothrips arisaemae. 23.—Chirothrips simplex. 24.—Limothrips cerealium. 25.—Calio- thrips indicus. 26.—Heliothrips haemorrhoidalis. 27.—Hercinothrips femoralis. August, 1974 Vance: Larvae of the Sericothripini 175 tively included the Chirothripini under the Thripini because of difficuhies in their categorization. Here, five tribes are tentatively rec- ognized in the Thripinae: the Chiro- thripini, Anaphothripini, Dendrothrip- ini, Thripini, and Sericothripini. Cer- tain combinations of larval features have been found to be characteristic of each tribe. Important characters at the tribal level include cuticular sculptur- ing; features of the antennal annula- tions, microtrichia, and sense cones; presence or absence of a posterior comb on abdominal tergite IX; and to a lesser extent the setal types and brown sclerotized body areas. Tribe Chirothripini Priesner ( 1949 ) The diagnostic features of Chiro- thripine larvae are: (1) cuticle with small pustules bearing minute micro- trichia, (2) body setae simple with certain ones knobbed (Fig. 64) (all reduced and pointed in Chirotlihps) (Fig. 45 and 62), (3) head and pronotum often with brown sclerotized areas (Fig. 44) (reduced in Cliiro- thrips) (Fig. 45), (4) antennal micro- trichia greatly reduced, (5) antennal sense cones short to moderately long (Fig. 23 and 24), and (6) eye facets small and not bulging at sides of head. The Chirothripini larvae resemble the Heliothripinae larvae in the reduc- tion of the annular microtrichia on the antennae, segment V in the first-stage larva being longer and having two an- nulations ( Fig. 11) (a trait found in most Heliothripinae but in no other Thripinae). The brown sclerotized areas of Limothiips resemble those found in many Heliothripinae. Two genera in this tribe occur in Illinois, Chirothrips and Limothrips. Both contain species that are grain feeders and can be serious pests. Material Examined.—INHS: Limo- thrips cereaUiim (Haliday); 1 larva II; 24 June 1953; Kenncy, Illinois. USNM: Chirothrips simplex Hood; 10 lar\'ae II, 1 prepupa; 21 October 1961; reared from Bouteloiia eriopoda; Las Cruces, New Mexico. Limothrips denticornis Haliday; 2 larvae I, 3 larvae II, 2 prepupae; 10 July 1959; on baj-ley; Northwood, North Dakota. Tribe Anaphothripini Priesner ( 1949 ) The diagnostic features of anapho- thripine larvae are: (1) cuticle cov- ered with large pustules and usually lacking microtrichia; (2) dorsal body setae pointed, knobbed, or blunt; (3) brown sclerotized body areas present in some species (Fig. 47 and 48); (4) posterior comb on abdominal tergite IX usually lacking (Fig. 66 and 67) (sometimes present in AnaplwtJirips); (5) annular microtrichia on antennae generally reduced (Fig. 12, 28, and 29); and (6) antennal sense cones moderately long to long. The status of the Anaphothripini has long been variously interpreted. Pries- ner (1957) included the members of this tribe within the Thripini. Gentile & Bailey ( 1968 ) considered the Ana- phothripini to be the most primitive of all thripine tribes, and Stannard ( personal communication ) is of the opinion that the Anaphothripini are close to the Heliothripinae. The lar\'ae of the Anaphothripini re- semble those of the Heliothripinae in cuticular sculpturing, the presence of brown coloration in some species, a reduction of antennal microtrichia, and other features. They resemble the Thripini larvae in cuticular sculpturing and in the posterior comb that is some- times present in Anaphothrips. Ami- pliothrips secticornis has brown sclero- tized areas on the pteronotum similar to those in the annulipes group of Seri- cothrips. Chaetanaphothrips possesses expanded setae similar to those of ?tericothrips. In Illinois the trilje Anapliothripini 176 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 is represented by Anaphothrips, Ap- tinothrips, Bregmatothrips, Chaetana- phothrips, Chilothrips, Oxijthrips, and Prosopothrips. Material Examined.—INHS: Am- phothrips secticornis Karny; 3 larvae I, 6 lar\'ae II; 21 January 1964; on short grasses; BarflF Peninsula, Sorling Valley, South Georgia Island. Aptinothrips nifus (Gmelin); 8 larvae I, 4 larvae II; 23 June 1933; on timothy heads; Champaign County, Illinois. Oxijthrips cannahensis Knechtel; 13 larvae I, 20 larvae II; August; on mari- juana; Henry and Morgan counties, Illinois. Chilothrips pini Hood; 5 larvae II; on Cottonwood; 15 October 1959; Park- land, Adams County, Wisconsin. Chilothrips sp.; 4 larvae II; on rot- ten wood and pigmy cypress duff; Deschutes County, Oregon, and Men- docino County, California. Tribe Dendrothiupini Priesner (1926fc-1928) The diagnostic features of dendro- thripine larvae are: ( 1) cuticle covered with minute microtrichia, resulting in a stippled pattern and forming larger pustules in transverse rows on the ter- minal abdominal segments (Fig. 71); (2) body setae generally simple but with certain ones terminally knobbed ( Fig. 74 ) ; ( 3 ) brown sclerotized areas lacking (Fig. 51); (4) antennal sense cones long (Fig. 35 and 36); (5) an- tennal microtrichia prominent and lo- cated between the annulations on seg- ment IV (larva I) (Fig. 13), as in the Sericothripini. Larval characters of the Dendro- thripini are well defined and easily delineated; the larvae are very similar to those of the Sericothripini. Cuticular sculpturing is similar to that of the Scricothripina, and setae are similar to those of the Scirtothripina. Random microtrichia on antennal segment IV are also diagnostic for larvae of the Dendrothripini and Sericothripini. The tribe Dendrothripini in Illinois includes one native genus, Leucothrips, and two genera introduced from Europe and Japan, Dendrotluips and Psetidodendroth rips, respectively. Material Examined.—INHS: Dendro- thrips ornatiis ( Jablonowski ) ; 5 larvae I, 3 larvae II; 23 August 1955; on privet; Champaign County, Illinois. Leucothrips piercei (Morgan); 1 larva I, 3 larvae II; 20 June 1967; on redbud leaves; Montgomery County, Illinois. Pseudodendrothrips mori (Niwa); 1 larva I, 4 larvae II; 25 October 1961; on Japanese mulberry leaves; McLean County, Illinois. Tribe Thripini Stephens (1829) The diagnostic features of thripine larvae are : ( 1 ) cuticle covered with small to large pustules ( Fig. 55 ) , often with microtrichia present; (2) dorsal body setae pointed ( Fig. 56 ) , knobbed, blunt, or terminally funneled; (3) brown sclerotized body areas usually absent; (4) posterior comb or teeth usually present on abdominal tergite IX except in Scolothrips (Fig. 75, 76, and 77); (5) antennal annular micro- trichia not reduced; and (6) antennal sense cones short to moderately long (Fig. 17, 37, and 38). The Thripini larvae resemble the Anaphothripini larvae in cuticular sculpturing and general body appear- ance. Generally, less diversification is found among closely related members of the Thripini than is usual among the members of other tribes. The tribe Thripini in Illinois includes Baliothrips, Ctenothrips, Dorcadothrips, FranklinieUa, Iridothrips, Microcephah- thrips, Odonotothrips, Plesiothrips, Rhaphidothrips, Scolothrips, Taenio- thrips, and Thrips. Material Examined.—INHS: Cteno- thrips bridivelli Franklin; 1 larva II; 11 August, 1974 Vance: Larvae of the Sericothbipini 177 Fig. 28-38.—Right antenna (except where indicated) of the second-instar larva. 28. — Anaphothrips secticornis. 29 —Oxythrips cannabensis. 30 — Echinothrips americanus. 31, Sericothrips annulipes. 32 —Sericothrips variabilis. 33 —Scirtothrips taxodii. 34 —Drepano- thrips reuteri. 35.—Dendrothrips ornatus. 36 —Pseudodendrothrips mori, left antenna. Ctenothrips bridwelli. 38.—Taeniothrips simplex. 37. 178 Illinois Natubal History Surn-ey Bulletin Vol. 31, Art. 5 July 1947; on Arisaema dracontium; La Salle County, Illinois. FrankUniella fusca (Hinds); 3 larvae II; 9 June 1949; Berlese collecting method; Mercer County, Illinois. F. parvtila Hood; 1 larva II; 20 June 1970; on bananas; Ciudad Chontalpa, Tabasco, Mexico. F. tritici (Fitch); 1 larva I, 9 larvae II; on flowers of yarrow and Culver's root flowers; Lake, Livingston, and Massac counties, Illinois. FrankUniella sp.; 12 larvae II, 3 pre- pupae, 2 pupae; May-July; on oats and from Berlese collecting method; Jack- son County, Illinois, and Friday Har- bor, Washington. Microcephalothrips sp.; 5 larvae II; 16 December 1949; on Spanish moss; Chiefland, Florida. Scolotlmps pallidus (Beach); 1 larva II; 28 July 1964; on cotton; Kewanee, Missouri. Taeniotlirips siinpJex (Morison); 10 larvae II, 7 prepupae, 11 pupae; July- August; on gladiolus; Champaign and Will counties, Illinois. Thrips impar Hood; 1 larva I, 5 larvae II; 16 July 1969; on jewelweed; Edward, Henry, and McLean counties, Illinois. Thrips phijsapus Linneaus; 1 larva II; December 1959; Recoaro, Italy. Thrips tabaci Lindeman; 1 larva I, 1 larva II; 25 April 1968; on clover; Champaign County, Illinois. Tribe Sericothripini Priesner (1926^-1928) The diagnostic features of serico- thripine larvae are: (1) cuticle covered with fine microtrichia, resulting in a stippled pattern over the abdomen and pteronotum; (2) cuticular pustules ab- sent or very reduced; (3) all or some dorsal body setae expanded and/ or fimbriate; (4) brown sclerotization lack- ing; (5) fourth antennal segment of first-instar larva densely covered with microtrichia. The tribe Sericothripini is divided into the subtribes Sericothripina, Scirto- thripina, and a new subtribe, the Echinothripina. Each of these groups is distinctive in certain larval charac- teristics, and each shows certain simi- larities with other tribes, indicating possible lines of relationship. Sericothrips, particularly the an- nulipes group, resembles the Anapho- thripini in such genera as Anaphothrips and Chaetanaphothrips. Most mem- bers of the annulipes group possess pteronotal sclerotized areas similar to those found in Anaphothrips secti- cornis. Sericothrips cingulatus has darker brown markings and small pustules reminiscent of those in the Anaphothripini and Chirothripini. Chaetanaphothrips has fanned (but not fimbriate) setae similar to those in Sericothrips. Scirtothrips and Drepanothrips show similarities to the Dendrothripini in setal features, coloration, and cuticular sculpturing. Subtribe Sericothripina Priesner (1957) Larvae of the Sericothripina are characterized by fan-shaped, fimbriate setae; minute cuticular microtrichia set on pustulelike bases on the terminal abdominal segments; and the absence of pustules elsewhere. An exception is Sericothrips cingulatus, in which all microtrichia are set on sinall pustules. Microtrichia in all Sericothrips species form transverse rows on the abdomen, especially on the terminal abdominal segments, similar to the rowed ordering of the larger pustules in other groups. Setal form in this group is unique among all thrips larvae and is an easily recognized diagnostic character. CaUothrips and possibly Chaetanapho- thrips have fan-shaped setae somewhat like those of the Sericothripina, but the setae of CaUothrips and Chaetanapho- thrips are smooth rather than fimbriate. The only genera in the Sericothripina August, 1974 Vance: Labvae of the Sericothripini 179 in Illinois are Seiicotliiips Haliday and Zonotlirips Priesner. Subtribe Scirtothripina Priesner (1957) Larvae of the Scirtothripina are char- acterized by setae expanded or fun- neled terminally only and by long, dense cuticular microtrichia in the ab- sence of cuticular pustules. Larvae of this subtribe are smaller than those of the Sericothripina and tend to have less ornamentation and less interspe- cific variation. Larval Scirtothripina have no hypodermal pigmentation, brown sclerotized areas, or setal basal rings; the setae are much simpler, and no cuticular pustulation is evident ex- cept for transverse rows formed by stippling on abdominal segments IX and X. Scirtothripina larvae resemble those of the Dendrothripini in their setae, both having combinations of long, terminally-funneled and short, pointed setae. Larvae of the Scirto- thripina can be easily identified (par- ticularly Scirtothrip.s) by their dense, long cuticular microtrichia and their lack of cuticular pustules. The genera included in this subtribe, according to Priesner (1957), are Charassothrips Hood, Dreponothrips Uzel, Enneo- thrips Hood, Ensifewthhps Bianche, Octothrips Moulton, Scirtodothrips Hood, Scirtothrips ShuW, and Seiicopso- thrips Hood. Subtribe Echinothripina, New Subtribe The proper placement of the genus Echinothrips in higher categories has long been in question. Moulton ( 1911 ) placed Echinothrips in the Heho- thripinae, and Medina as late as 1961 still considered this to be the best placement. Priesner ( 1957 ) , however, considered this genus to be in the Thripini because of imaginal endo- thoracic morphology, and Stannard (1968) transferred Echinothrips into the Sericothripini because of the pres- ence of abdominal microtrichia and the lack of fusion of the fore vein to the costa in the fore wing of the adults. The larval characters of Echinothrips support Stannard's placement of the genus. Similarities of Echinothrips larvae to the larvae of other Serico- thripini genera can be seen in cuticular microtrichia, fimbriate setae, antennal shape and sense cones, and extra micro- trichia on antennal segment IV of first- stage larvae. Echinothrips differs in its unexpanded and more elongate body setae, larger and more elongate body size, positioning of head setae HI, and loss of pronotal setae P3. Generally, Echinothrips most closely resembles the Sericothripina, but be- cause of the differences described, the genus has been placed in its own sub- tribe. Wilson ( 1971 ) delimits a group of closely related genera that he calls the Echinothrips complex, including Cercyothrips Morgan, Echinothrips Moulton, Enneothrips Hood, Plesiopso- tlirips Hood, Plesiothrips Hood, and Ptericlotlirips Priesner. Some of these he placed with the Thripini and others with the Sericothripini. Wilson feels that this group is transitional between the Sericothripini and the Thripini and that possibly it merits tribal status. Tlie only genus included here in this sub- tribe is Echinothrips Moulton. Drepanothrips Uzel (1895) Larva IL—Body color yellow. An- tennal segments, tibiae, bases of femora, setae, and setal basal rings light brown to brown. Apices of antennal segments I and II and base and apex of segment III pale gray. Eyes red. Antennae each seven segmented ( Fig. 34 ) ; longer sense cone on seg- ment IV, and sense cones on segments V and VI moderately long and slightly blunted; all of equal length. Segment II with a pair of terminally funneled setae; segment III with six annulations. 180 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 the distal three with short niicro- trichia; segment IV with five annula- tions, all with longer microtrichia. Head (Fig. 52) longer than wide. Eyes with four large facets bulging at sides of head. Mouth cone moderately blunt. Head with four pairs of dorsal setae; HI, H3, and H4 subequal and terminally funneled. Pronotum longer than wide with seven pairs of terminally funneled setae; P6 and P7 somewhat longer than P1-P5. Mesonotum with seven pairs and metanotum with five pairs of funneled setae, all of nearly equal length. Abdominal tergite I with two pairs and tergites II-VIII each with three pairs of funneled setae; Al, A2, and sometimes A3 on tergite IX (Fig. 70 ) funneled, and all subequal to equal in length. Abdominal tergite X with three pairs of setae, Al funneled. Almost all dorsal body setae termi- nally funneled and of moderate length. Bases of setae with faint brown rings. Abdominal and pteronotal cuticle with dense stippling and fine microtrichia, which are shorter and less obvious than those on Sciiiothrips and longer than those on Seiicothiips, stippling forming transverse rows on abdominal segments IX and X. Segment IX lacking a posterior comb. Diagnosis.— D repanothrips larvae most closely resemble Scirtothrips larvae from which they can be dis- tinguished by the dorsal body setae, all of which are terminally funneled, while only a few characteristic ones are funneled in Scirtothrips. The cu- ticular microsetae are shorter and less dense in Drepanothrips than they are in Scirtothrips. Larvae of Drepano- thrips difi^er from those of other Serico- thripini in having terminally expanded setae, the setae of the other genera being either totally expanded or long and un- expanded. Dendrothrips and Pseudo- dendrothrips, which resemble Drepano- thrips in the larval stages, can be dif- ferentiated by their lack of cuticular microtrichia and by their having only certain dorsal body setae funneled. The genus contains only one species, D. reuteri, in Illinois. Drepanothrips reuteri Uzel (1895) (Fig. 34, 52, and 70) Larva II.—Body light yellow to yel- low. Antennae, tibiae, bases of femora, and setal basal rings light brown; an- tennal segments II, V-VIII, and apex of IV often darker brown. Apices of antennal segments I and II and base and apex of segment III very pale gray. Eyes dark red. Most body setae slender, terminally funneled or dilated, and subequal in length ( 14-19 fim ) . Bases of setae with faint unraised brown rings. Dorsal sclerotized areas lacking. Stippling forming transverse rows only on ab- dominal segments IX and X. Measurements of the D. reuteri larva II are shown in Table 6. Diagnosis. — D. reuteri occurs on grapevines {Vitis sp. ), of which it Table 6.—Measurements, in microns, of three Drepanothrips reuteri larvae II. Character Length ^Range Mean Range Antennal segment I II III IV V VI VII ^ Antenna Head Pronotum Body Setae HI H4 P7 A(IX)1 A(IX)2 Ventral setae (IX) 19" 28-31 42-46 42-46 8-11 8-9 16 163-178 70-78 93-124 660-825 16 16-19 16-19 14-16 17-19 15 171 765 22-23 22-23 22 17-20 12-14 9 6 78-85 124-140 i I " A single measuremeni indicates that all such identical. St August, 1974 Vance: Larvae of the Sericothkipini 181 has been reported to be a pest. Bailey ( 1942 ) gave an account of the biology of this thrips and discussed the litera- ture concerning it. This species has been recorded only once in Illinois, two adult females having been taken in Fig. 39-48.—Head and pronotum (except where indicated 1 of the second-instar larva. 39. — Aeolothrips vittipennis. 40.—Merothrips morgani. 41.—Heterothrips arisaemae. 42. — I Phlaeothripid (Tubuliferal . 43. — Heliothrips haemorrhoidalis. 44.—Limothrips cerealium, j head, pronotum, and left foreleg. 45. — Chirothrips simplex, head, pronotum, and left foreleg. i 46.^-Caliothrips indicus. 47.—Oxythrips cannabensis. 48.—Anaphothrips secticornis. 182 Illinois Natltral History Survey Bxn.LETiN Vol. 31, Art. 5 Urbana from a sparrow nest built in a grape arbor. Material Examined.—INHS: 3 larvae II; 23 August 1965; on grape; col- lected by K. Stahlik; Selma, Fresno County, California. Echinothrips Moulton (1911) Larva II.—Cuticular color usually yellovi? to orange. Antennal segments, tibiae, bases of femora, and setae gen- erally light brown. Eyes red. Antennae each seven segmented ( Fig. 30 ) ; longest sense cone on seg- ment IV, sense cones on V and VI long and pointed; segments II and III each with two pairs of fimbriate setae; seg- ment III with five annulations, none with microtrichia; segment IV with five annulations, all with microtrichia. Head (Fig. 54) wider than long. Eyes with four large facets bulging at sides of head. Mouth cone moderately blunt. Head with four pairs of dorsal setae, all long and fimbriate; HI lo- cated more posteriorly than usual in most known thrips larvae and almost opposite to H4; H3 and H4 equal and shorter than HI. Pronotum (Fig. 54) wider than long with six pairs of fimbriate setae; P3 lacking; PI, 2, 4, and 6 all longer than P7. Mesonotum with seven pairs and metanotum with four pairs of long fimbriate setae of varying lengths. Setae Al and 2 of abdominal segment IX long; A3 of varying length, some- times reduced (Fig. 73). Segment X with three pairs of dorsal setae; Al and A3 long and fimbriate. Most dorsal body setae fimbriate and long, the setal lengths on abdominal tergites sometimes varying greatly. Cu- ticle with minute microtrichia sparsely scattered on abdominal tergites, micro- trichia becoming pustulelike and form- ing transverse rows on the terminal abdominal segments. Abdominal seg- ment IX lacking a posterior comb. Larva I.—Cuticle yellow to orange; hypodermal pigment lacking. Anten- nal segments I, III, and most of IV, tibiae, and bases of femora generally light brown; segment II, apex of IV, and all of V-VII darker brown. Eyes red. Antennae each seven segmented; su- ture between IV and V usually distinct. Sense cones on segments IV-VI as in larva II, but longer (Fig. 16). Seg- ments II and III each with a pair of long fimbriate setae. Segment III with five annulations, with minute micro- trichia present ventrally. Segment IV with six annulations; microtrichia pres- ent randomly on and between annula- tions but less dense than in Scirto- thrips. Apical segment not narrowed tenninally. Chaetotaxy similar to that of larva II, except posteroangular setae (P7) lacking, the mesonotum with four pairs of setae, the metanotum with three pairs of setae, and abdominal segment IX with two pairs of dorsal setae. Integument with stippling, as in larva II, but fainter. Diagnosis. — Echinothrips larvae can be easily recognized by their long fim- briate setae and elongate body shape, which are unique among the Thripinae in Illinois. Antennal and cuticular sculpturing are similar to those of Sericothrips, but setal length and type, body shape, placement of setae HI (more posterior in Echinothrips), and loss of one pronotal setal pair (P3) differ from those of Sericothrips. These features distinguish Echinothrips from all other genera. The only other thripine genus in Illinois possessing long setae similar to those in Echino- thrips is ScoJothrips. Interspecific variation in Echinothrips is very limited in the two species con- sidered, E. americanus and E. suh- fJavus. In the one slide of E. subflavus studied, body dimensions and setal lengths were larger than those in August, 1974 Vance: Larvae of the Sericothripini 183 E. americanus. However, considerable variation in setal lengths was found in americanus; so the extent of variation in both species will have to be investi- gated before setal measurements can be used as a diagnostic feature. Echinothrips americanus Morgan (1913) (Fig. 16, 30, 54, and 73) Larva II.—Cuticle yellow to orange. Antennae, tibiae, bases of femora, and Fig. 49-56.—Head and pronotum of the second-instar larva. 49. — Scirtothrips niveus. 50.—Scirtothrips taxodii. 51.—Dendrothrips ornatus. 52.—Drepanothrips reuteri. 53. — Sericothrips annulipes. 54.—Echinothrips americanus. 55.—Taeniothrips simplex. 55. — Scolothrips pallidas. 184 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 setae brown; apices of antennal seg- ments I and II and base and apex of III light brown. Eyes red. Most dorsal setae long (50-70 jjm) and fimbriate for most of their length; others (H2; Msl, 2, 5, and 6; and Mtl) shorter (20-30 ^'Hi). Light brown spot present on head anteriorly. Cuticle with large stippling on abdomen forming transverse rows and becoming finer and randomly distributed on pterono- tum and posterior portion of pronotum. Measurements of the E. americanus larva II are shown in Table 7. Table 7.—Measurements, in microns, of five Echinothrips americanus larvae II. Character August, 1974 Vance: Larvae of the Sericothripini 185 fonning tr;ins\erse rows and becoming finer and randomly distributed on pteronotum and posterior portion of pronotum. Measurements of the E. siibflaviis larva II arc shown in Table 9. Table 9.—Measurements, in microns, of one Echinothrips subflavus larva II. Character 186 Illinois Natural History Subvey Bulletin Vol. 31, Art. 5 of terminally funnelcd setae; segment III with six annulations with fine micro- trichia present on the distal four and some microtrichia scattered between the annulations; segment IV with five annulations, with longer microtrichia . . '^'9-. 57-67.—Abdominal segments Vlll-X of the second-instar larva. 57. — Aeolothrips *'f*'P^"""- 58.—Merothrips morgan!. 59.—Heterothrips arisaemac. 60.—Caliothrips indicus. ^Ji , ^^1 P''' 'Tubulifera). 62.—Chirothrips simplex. 63.—Heliothrips haemorrhoidalis. °*^ —l-"no»n"Ps eerealium. 65.—Hercinofhrips femoralis. 66.—Oxythrips eannabensis. 67.—Anaphothrips sccticornis. I August, 1974 Vance: Larvae of the Sericothripini 187 present on and randomly bet\\een the annulations; segment VII tapering apically. Chaetotaxy similar to that of larva II, except the posteroangular setae lack- ing, mesonotum with four pairs and metanotum with three pairs of setae, and abdominal segment IX with two dorsal pairs and one lateral pair of setae. Integument with microtrichia, and resultant stippled pattern fainter than in larva II. Diagnosis. — Scirtothrips larvae can be distinguished from the larvae of other sericothripines by their long dense cuticular microtrichia and by their simple reduced dorsal body setae, only a few of which are long and ter- minally funneled. Drepanotluips and Sericothrips have less dense and shorter cuticular microtrichia and all setae either terminally funneled or fanned. Scirtothrips resembles Dendroth rips in having small simple setae with only certain ones longer and terminally fun- neled, but larvae of the latter genus lack the dense cuticular microtrichia of Scirtothrips. Morphological characters used to separate the lar\'ae of Scirtothrips are uncertain. The extent of intraspecific variation in the species is not known due to a lack of specimens. Host-plant data and associated adults should be used where possible to supplement lan'al identifications. KEY TO THE MATURE LARVAE II OF SCIRTOTHRIPS 1. Dorsal setae HI, H4, P7, A(IX) 2, and A(X)1 all terminally funneled; HI and H4 both longer, about 23 /xm (Pig. 49 J ; body color yellow; found on dogwood niveus At most, only dorsal setae HI and P7 funneled; HI and H4 shorter, about 15 ^m (Fig. 50); body color yellow or orange; found on red cedar or on cypress 2 2. Body color usually orange; setae A(1X)1 and 3 significantly shorter than A(IX)2; found on red cedar brevipennis Body color yellow, sometimes with orange subintegumental pigment; setae A(IX)1 and 3 long (19 and 23-25 ^m) and subequal to A(IX)2 (Fig. 72); found on cypress. . .taxodii Scirtothrips brevipennis Hood (1914) Larva II.—Body pale orange to yel- low-orange, sometimes with darker orange pigmentation. Antennal seg- ments I-IV brown; apices of segments I, II, and III pale gray; segments V-VII darker brown. Tibiae, bases of femora, and anterior median cephalic spot brown. Eyes red. Most setae simple, pointed, and short; HI and P7 longer and funneled; A (IX) 2 pointed and decidedlv longer than A(IX)1 and A (IX) 3. ' Cuticle with fine dense microtrichia. Measurements of the S. brevipennis larva II are shown in Table 10. Table 1 0.—Measurements, in microns, of two Scirtothrips brevipennis larvae II. 188 IixiNOis Natural History Surney Bulletin Vol. 31, Art. 5 A(X)1 pointed instead of terminally funneled. S. hrevipenni.s larvae are separated from those of taxodii by hav- ing orange body color (usually yellow in taxodii) and shorter setae (Al and A3) on abdominal segment IX than taxodii larvae have. S. brevipennis is found on eastern red cedar (Juniperus virginiana ) . Material Examined.—INHS: 2 larvae II; June; on red cedar; Jolmson and Pope counties, Illinois. Scirtothrips niveus Hood (1913) (Fig. 49) Larva II.—Body yellow with darker yellow pigmentation. Antennae, tibiae and bases of femora light brown. Apices of antennal segments I and II and base and apex of III pale gray. Eyes red. Most setae simple, fairly short ( 12 f,.m), and pointed; HI, H4, P7, A(IX)2, and A(X)1 all longer and funneled. Cuticle with fine dense microtrichia. Measurements of the S. niveus larva II are shown in Table 11. Diagnosis.—S. niveus larvae can be distinguished from other Scirtothrips Table 1 1 .—Measurements, in microns, of one Scirtothrips niveus larva II. Character August, 1974 Vance: Larvae of the Sericothripini 189 Larva I.—Body pale yellow, often with red-orange body pigment. Anten- nal segments I and II light brown; seg- ments III and proximal portion of IV brownish orange; apex of IV and seg- ments V-VII all darker brown; tibiae and bases of femora brown. Eyes red. Most setae pointed and short ( 8 /un ) ; only HI knobbed. Posteroangular setae lacking. Anterior median cephalic spot Fig. 68-77.—Abdominal segments Vlll-X (except where indicated) of the second-instar larva. 68. — Sericothrips campestris. 69.—Sericothrips annulipes, abdominal segments IX and X. 70. — Drepanothrips reuteri. 71.—Dendrothrips ornatus. 72.—Scirtothrips taxodii. 73. — Echinothrips americanus. 74.—Pseudodendrothrips mori. 7 5.—Taeniothrips simplex. 76.— - Ctenothrips bridwelii. 77.—Scolothrips pallidus. 190 Illinois Natural History Survey Bulletin Vol. 31, Art. 5 lacking. Cuticle with very fine micro- trichia. Measurements of the S. taxodii larva I are shown in Table 13. Table 13.—Measurements, in microns, of two Seirtothrips taxodii larvae I. August, 1974 Vance: Larvae of the Sericothripini 191 \arying degrees and of varying lengths. Setal bases usually with f-nnt brown rings (much larger and more promi- nent in annulipes, ptdchellus, and cin^idatiis and to a lesser degree in oaiiabilis). Integument with dense stippling resulting from very fine micro- trichia; stippling forming transverse Fig. 78-89.—Abdominal segments III and IV (except where indicated) of Sericothrips species. 78.—S. cingulatus. 79.—S. annulipes. 80.—S. pulchellus. 81.—S. variabilis. 82.—S. baptisiae. 83.—S. campestris. 84.—S. beachae. 85.—S. tiliae. 86.—S. nubilipennis. 87.—S. sambuci. 88.—S. langei. 89.—S. annulipes, meso- and metanotum. 192 Illinois Natural History StmvEY Bulletin Vol. 31, Art. 5 rows on aljcloniinal segments, particu- larly on segments IX and X (minute pustules present in cin