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DESCKIPTIOlSr OF A NEW SPECIES OF
ASELLUS.

By 0. P. HAY.

Asellus militaris. {Sp. not.)

Length of male 17 mm., of female 11 mm. Color brown, ornamented

with irregular shaped yellow spots, somewhat symmetrically arranged on

each side of the median line. Feet and caudal stylets with a tinge of rose.

Upper surface of the body covered with minute scattered hairs. All the

free margins of the body abundantly furnished with slender spines
;
these

longest on the lateral margin. Head narrow, only about one-half the width

of the first thoracic segment; the anterior margin concave; antero-lateral angles

obliquely truncated ; lateral margins diverging posteriorly, with a small

outwardly projecting lobe at the posterior angle ; this lobe furnished with

several short spines. Eyes comparatively small. Anterior segments of

thorax concave in front, convex behind ; becoming less so to fifth segment,

whose anterior and posterior margins are nearly straight. Sixth and sev-

enth segments convex in front, concave behind, the concavity being deepest

in the seventh. All the thoracic segments after the second about, the same

width ; the second a little narrower than the succeeding segments ; the first

about three-fourths as wide as the widest. Antero-lateral angles of first

segment excavated and filled by the broad epimera. Second segment very

slightly notched in front. In the succeeding segments this notch is pushed

further back and becomes deeper, especially in the last three. As the notch

becomes deeper, the antero-lateral angle is lengthened and turned back-

ward. The epimera again make their appearance in the fifth, sixth, and

seventh segments, only partially filling the lateral notches. Postero-lateral

angles of all the thoracic segments rounded.

Abdomen sub-orbicular ; width and length equal ; anterior and pos-

terior angles quite well marked. Posterior margin excavated at insertion

of caudal stylets, prolonged behind into a median lobe. This, in the male,

reaches back scarcely one-third the length of the pedicel of the caudal sty-

lets, but in the female about one-half the length of the pedicel. Width of

abdomen less than that of any of the thoracic segments, except the first and

second, about equal in width to second. Antennulse shorter than the pe

duncle of the antennae ; basal segment short, a little curved and having a

diameter nearly three times that of the next segment ; second segment.



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longer than the first: third sub-equal to the first. Flagellum equal to the

peduncle and consisting of about twelve segments.

First three segments of the antennae short ; fourth as long as the three

preceding; fifth as long as the second, third and fourth together ; flagellum

long, reaching baok three-fourths the length of the thorax, and consisting of

about seventy-five segments.

Right mandible with a single dentigerous lamella furnished with four

obtuse teeth. Left mandible with two dentigerous lamella;, each with four

obtuse teeth Palpus consisting of three segments; the first clavate ; the

second widest in the middle, its inner margin being straight and its outer

formed by two straight lines meeting at an obtuse angle at the middle of

the segment ; last segment falcate, furnished with numerous plumose hairs

along its outer concave margin.

Palpus of maxilliped with five segments. The first very short. The
second three times as long as the first and rather broader than long, with

the inner margin straight and the outer curved. Third segment short,

broadest just above the proximal articulation, becoming narrower distally.

Fourth segment clavate and bent inward at the base. Last segment short

and only half as wide as the preceding. All the segments provided with

scattered hairs along their outer margin and crowded with similar hairs

along the inner margin.

Propodus of the first pair of legs in the male ovate, nearly two-thirds

as wide as long ; the palmar margin slightly convex, armed with a stout

conical tooth in the middle, and at the posterior angle with another short ob-

tuse one, surmounting a rough process of the body of the propodus. There
are thus really two stout teeth on this margin. Dactylus with its claw
reaching beyond the palmar margin, curved strongly, and armed with about
fifteen teeth appressed towards the tip.

In the female the first propodus is more slender, being one-half as wide
as long. Palmar mai'gin nearly straight and armed with several slender

spines, and near the posterior angle with one moderately strong acute tooth.

Dactylus long, curved, and armed with about eight teeth longer than those

of the male. Dactylus terminating in a claw, which extends beyond the

palmar margin.

Anterior genital appendages of the male consisting each of two seg

ments, the fir.t three-fourths the length of the second, sub-quadrate, with

four curved spines along the inner margin ; the second segment ovate, with

an obliquely truncated extremity, which, as well as the adjacent parts of

the inner and outer margins, is sparsely cilated. Posterior genital ap-

pendages consisting each of a peduncle and two rami. The peduncle about
as broad as long, outer margin straight, inner margin approaching the

outer distally by a broad curve. Inner ramus navicular, notched at the

distal extremity. Outer ramus bi-articulate ; first segment triangular ; sec-

ond linguiform, twice as long as broad, with the outer margin and the lower

portion of the inner margin furnished with long plumose hairs. Caudal
stylets of the male as long as the abdomen , the peduncle a little less than

two-thirds as wide as long, expanding distally, where it is excavated for the

insertion of the rami. The rami are ovate, moderately acute, width about

one-third of the length : the outer ramus about two-thirds as Ions as the



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inner, and both tipped with a brush of long hairs, and fringed with numer-
ous setae : as are also the margins of the peduncle

Caudal stylets of the female only two- thirds the length of the abdo-

men, peduncle wider proportionally than in the male, and obtriangular.

Rami more lanceolate in outline, scarcely a fourth as wide as long : the

outer nearly as long as the inner, which is nearly a third longer than the

peduncle.

Found in large numbers in shallow pools of a slow prairie stream, near

Abingdon, Knox county, Illinois.

This fine large species is probably nearly related to AscHus mtermedms,
Forbes. It diflfers, however, from all the forms of this that I have seen,

not only in its much greater size, but also in some other important respects.

The head is much narrower in the present species than in mtermedms. The
abdomen is narrower in this than the species described by Prof. Forbes, as

compared with the width of the thoracic segments. The thoracic segments

in specimens of undoubted intermedius which I have, increase in width from

the first to the last, while in A. militaris they are, after the second, of uni-

form width. The two posterior segments in A. militaru are also much more
deeply concave along their posterior margin than in the other species men-
tioned. The propodus in the present species is broader than in mtermedms,
but I have specimens of an AseUus from Prof. Forbes, which he provisionally

regards as A. mtermedms, in which the propodus is rather broader than in

my species. The genital plates, however, differ much from those of A. mil-

itaris. The plates, again, are, in militaris, almost exactly as in the typical

specimens of intertnedius. The doubtful forms of intemedkis, however, differ

from the present species in the width of head, abdomen, concavity of pos-

terior thoracic segments and in the form of the caudal stylets.

My thanks are due Prof. Forbes for specimens of his two forms of ^.
Intermedius and for the use of microscope slides.


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