82 THOMAS SAY FOUNDATION" 



Segment 10 divided above in the usual manner ; a blackish 

 V-mark on its base above marks the base of the U-shaped 

 supra-anal process; the rear lobes of 10 above are flat, 

 bluntly triangular, sparsely fringed on the hind margin 

 with incurving hairs and beset with short stout pegs on 

 the dorsal surface. 



Female. Subgenital plate very large, about as wide as 

 long, yellow, covered with fine long hairs, as wide as ab- 

 domen and extending beyond hind margin of segment 

 nine ; outer margin very broadly rounded. 



Distribution. — Grant, Colo. ; Lawn Lake, Estes Park, 

 Colo., August 27, 1919, 10,500 ft. (P. W. Claassen) ; Tol- 

 land, Colo. (G. S. Dodds). 



Perla postica Walker. 



(Plate 11, fig. 3.) 



1842. Perla postica Walker, Cat. Nenr. Ins. Brit. Mus., p. 144. 



1861. Perla postica Hagen, Syn. Nenr. N. Amer., p. 23. 



1904. Perla postica Banks, Proc. Ent. Soc. Wash., 6:205. 



1907. Perla postica Banks. Cat. Xenrop., p. 12. 



1921. Perla subvarians Banks, Bull. Mis. Comp. Zool., 64:317. 



Length 10 to 15 mm. ; expanse, 33 to 39 mm. 



Color blackish or brownish, including antennae and pal- 

 pi. Yellow triangular spot upon the occiput is prolonged 

 forward between the ocelli in a usually parallel sided 

 (sometimes tapering) tip and there are two oblique yel- 

 lowish marks upon the sides of the clypeus before the 

 bases of the antennae. Prothorax quadrangular wider 

 than long with sides parallel and angles more or less 

 acute. The yellow middorsal stripe upon the dorsum 

 widens to rearward. Meso- and metathorax brown. Legs 

 pale brown, darkened somewhat toward the knees where 

 there is the usual yellow transverse pale ring across the 

 tip of the femur. Wings subhyaline with brown veins, 

 and in some specimens (all females, as yet noted) a wash 

 of brownish covers the rear third or fourth of the hind 

 wings, this being wholly confined to the folded anal area. 



Abdomen brown, the two apical segments more or legs 

 yellow (more in the female) : tails brownish to the base. 



Male. Abdominal segments little modified before the 

 10th; 7, 8 and 9 successively a little more prolonged be- 

 neath, and 9 abbreviated dorsally, but the subgenital pro- 

 longation of 9 is very moderate, not scoop-like, and hardly 

 set off by grooves at the sides. Segment 10 is cleft above 

 and the rear angles of the cleft are elevated into strap- 

 like lobes that are very hairy, beset also with stout short 

 spinules on their forward margin, and rounded on the 



