OP PHILADELPHIA. 51 



three brownish spots on the costal margin ; feet whitish, joints a 

 little dusky ; tergum blackish at tip, pale at base. 

 Length less than one-fifth of an inch. 



The number, form and position of the wing spots, are similar 

 to those of Sciara punctata, Fabr., it differs, however, from that 

 insect, in addition to other peculiarities, by the color of the tho- 

 racic lineations. 



2. R. ALTERXATUS. — Costal margin of the wing beyond [28] 

 the middle with three fuscous spots alternating with white ones- 

 Inhabits Pennsylvania. 



Body blackish-fuscous ; thorax with three black lines, of which 

 the intermediate one is double ; feet short ; wings hyaline, con- 

 necting nervures slightly margined with fuscous spots on the cos- 

 tal r^argin, placed one on the middle of the length, then a white 

 one which is very conspicuous on the edge of the wing, then a 

 brown one, then another white one divided into two compartments 

 by a nervure, then a third brown one terminated at the tip of the 

 wing by a third white spot. 



9 Length to the tip of the wings a quarter of an inch. 

 The habit differs from that of the other species I have seen. 



SIMULIUM Latr. 



S. VENUSTUM. — -Black; thorax, two perlaceous spots before, 

 and a larger one behind ; poisers black, capitulum bright yellow, 

 dilated. 



Inhabits Shippingsport. 



Body black ; wings whitish, with yellow, and iridescent reflex- 

 ions. 



Male, eyes very large, separated only by a simple line, dull 

 reddish yellow, inferior half black ; thorax velvet-black, a brighi 

 oblic{ue, perlaceous, dilated line each side before, and a large per- 

 laceous [29] spot or band behind ; sides beneath varied with per- 

 laceous ; feet, tibia above, and first joint of the four posterior 

 tarsi, white ; abdomen with an oblique perlaceous line at base, 

 and two approximate, lateral, perlaceous ones near the tip. 



Female. — -Eyes moderate ; thorax plumbeous-black, immacu- 

 late ; scutel black : abdomen whitish beneath. 



This very pretty species, perched in considerable numbers on 

 our boat at Shippingsport, Falls of the Ohio. It ran with con- 

 1823.] 



