32 NEW YORK STATE MUSEUM 



covered with a thin, filmy growth of algae, with abundant nets 

 of the caddisfly seine-maker, H y d r o p s y c h e ; and the broken 

 edges of the floor ledges are fringed with black masses of black fly 

 larvae, Simulium. Sim u Hum and Hydropsyche 

 are fixed in their places, but Chirotenetes wanders about 

 freely over the ledges, clinging securely even in the swiftest 

 water, keeping of necessity head up stream, moving by short 

 quick dashes, effected by sharp strokes of its powerful tail fin 

 and gill covers, moved synchronously. It is also found in the 

 stiller pools at the sides of the current, in which dwell other may- 

 flies of the genera C a e n i s and B a e ti s; and also among 

 the rocks in the current, under which cling other nymphs of 

 H e p t a g e n i a , Blast ur us and Choroterpes. 



Measurements. Length, imago and subimago, <$ 11-12 mm.; $ 

 12-1.'). H mm.; setae additional, subimago, J 1 13; $ 11; imago, < 23; 

 $ 20 ; fore leg of <$ and $ subimago and of $ imago two thirds as 

 long as body, of imago seven eights as long as body. 



Subimago. Color brownish tinged, with tawny changing to 

 rufous with age. with a pale middorsal line the entire length of 

 the body dilated and overspreading the dorsum of the meso- 

 thorax. Fore legs rufous, with whitish or pale lutescent tarsi, of 

 which the sutures are narrowly marked with brown in the male. 

 Middle and hind legs wholly pale. Wings subhyaline, paler on 

 the inner margin, all crossveins bordered with ashy brown (pi. 5, 

 fig.2). Abdominal segments pale brown, the apical margin with 

 a transverse apical line and the lateral margins with a longi- 

 tudinal dash of darker brown; last segment and setae and ap- 

 pendages wholly pale. The ventral prolongation of the ninth 

 segment in the $> is bifid apically as in the imago, but not declined 

 at the tip. The eyes of the male are not contiguous, and the for- 

 ceps limbs are straight, and surpass the tip of the rudimentary 

 middle seta by the length of the latter. 



imago. Thorax brownish, abdomen rufescent; head pale 

 lutescent below, rufescent above between the black-ringed ocelli 

 and the eyes. Thorax darker brown above and below and paler 

 along the sides, but without definite markings. Fore legs bright 

 rufous, with wholly white tarsi ; middle and hind legs wholly 

 pale whitish. Wings hyaline. Abdominal segments rufous, trans- 

 verse apical carinae and lateral margin distinctly lineate with 

 blackish brown ; segment 10 paler, yellowish rufescent, strongly 

 produced backward above in a 'broad obtusely truncated superior 



