210 ROBERT H. WOLCOTT: 



2. ATAX ACULEATUS KOENIKE. 



Atax crassipes juv. Claparede, 68; 471, PI, XXXIII, f. 1-3. 

 Atax aculeatus Koenike, 90; 138: id., 95d; 386, f. 13: Piersig, 96; 40, 

 footnote: id., 97; Lief. 1, 59, PI. I, f. 3. 



A. aculeatus is very closely related to A. crassipes and can best be 

 described by comparing it directly with that species. It is similar in form, 

 but so far as the author's observation goes never reaches as great size, the 

 males attaining a length of from 0.5 to 0.6 mm., the females 0.65 to 

 0.75 mm. 



The mandibles are similar in form as is also the maxillary shield. The 

 eyes are very large, black and rather close together. 



The palpi share in the resemblance, though they are apparently a 

 trifle more slender and are proportionately longer. 



The epimera occupy even more of the under surface of the body and 

 in the male the four groups are almost in contact. 



The legs are very long as in A. crassipes and the proportions similar, 

 though those of A. aculeatus seem slightly stouter than in the allied 

 species. The sixth segment is, however, somewhat longer in III and 

 exceeds 4. In I, 4 is the longest and 5 and 6 approximately equal to each 

 other, while both exceed 3; 6 is also not quite so slender as is the case 

 in A. crassipes and is less curved and a little dilated at the tip. The 

 arrangement and length of the spines on the legs are practically the same 

 in the two species. The claws are similar. 



The genital field in the present form is characteristic and markedly 

 different from that of A. crassipes. There are but ten acetabula instead 

 of twelve, in the male situated on two kidney shaped plates which flank 

 the genital cleft. On each side two anterior acetabula are placed one directly 

 behind the other, and are separated by an interval from the three pos- 

 terior, of which the two anterior lie side by side. The cleft is longer than 

 in A. crassipes and in the case of all specimens on slides gapes widely. 

 In the female the single lateral plate is divided into two, the anterior of 

 which is pouch-shaped with the neck of the pouch directed anteriad, while 

 the posterior is similar in outline but inverted. The former has two 

 acetabula, the latter three. The ovipositor is prominent and of character- 

 istic form. From each side of the genital opening projects a plate which 

 anteriorly and — since the genital area is on the posterior surface of the 

 body — also, ventrally, is produced and turned outward forming a conical 

 process, at the top of which is articulated a short, thick, sharply-pointed 

 spine. At the base of this, internally, is a small sharply-pointed process, 

 and from the posterior — and dorsal — margin projects a longer, tapering 

 and sharply pointed process, both of these processes being not set into 

 sockets, bu^t apparently continuous with the rest of the plate. By the 

 apposition of these two plates, they are able, probably, to serve together 

 as an ovipositor. 



