AQUATIC IXiSECTS IN NEW YORK STATE 375 



treme base of tlie tibiae yellowish, with a single short spur on 

 the fore tibiae, aud a pair of longer ones on middle and hind 

 tibiae [pl.38, fig.8]. Fore and middle tarsi slender, hind ones 

 widened, all claws trifid [pl.38, fig.8, 17]. Wings hyaline or 

 slightly tinged; the anterior yeins thickened, the remainder 

 slender [pl.3G, fig.7]. Knob of halteres orange yellow. The 

 male genital organs are short though rather complex, consisting 

 of a pair of outer sheaths, then a pair of elongate blunt pro- 

 cesses, within which are two pairs of hooks; the outer, shorter 

 l^air are incurved and clawlike; the longer, inner pair are 

 slender, with some outwardly projecting hooks. Length 3.5 to 

 4mm. 



Female. Eyes with a small deep sinus on each side, just about 

 the base of the antennae, above which the front is a little longer 

 than wide, and a little wider above than below. Face a little 

 wider than the narrow part of the front, the sides parallel, its 

 surface gently and evenly convex, clothed with white hairs; 

 antennae tapering more than in the males, the first two joints 

 yellowish. Basal joints of palpi stouter. Facets of eyes uni- 

 formly small, the eyes much smaller and the posterior orbits 

 conspicuous. Thorax like the head, opaque gray pruinose. 

 Metanotum with three slender, deep brown or black stripes, the 

 lateral ones gently incurved back of the anterior knoblike dila- 

 tion. Abdomen velvet-black, the second segment (or the part 

 beneath the leaflike margins of the first) and the positerior 

 margins of three following segments (except at the center), 

 opaque gray or grayish white; the remaining segments, and leaf- 

 like sides of the first, lightly pruinose; venter gray; in some 

 specimens with a small black or grayish triangular spot on cen- 

 ter of the dorsum of segments 3, 4 and 5. The legs grayish, in 

 some specimens quite pale; the tips of some or all the tibiae 

 usually, and the tarsi nearly always, black, except the bases of 

 hind metatarsi and sometimes the middle also, which are yellow. 

 The tibial spurs and hind metatarsi as with the male. Tarsal 

 claws simple [pl.38, fig.20]. Wings as with the male. Knob 

 of halteres yellowish white. Length 3 to 4mm. 



I have compared this species with Hagen's type, (larvae, pupae 

 and adults) and find that they agree perfectly. The apparent 

 discrepancy' in comparing Hagen's description^ with the one 

 given above is due to the fact that Hagen described his from 

 bottled material. His description agrees very well with al- 

 coholic material of this very common Ithaca species. Hagen 

 was in error in regard to the number of respiratory filaments of 



iBost. Soc. Nat. Hist. Proc. 20:305. 



