[Berliner Entomolog. Zeitschrift Bd. XXVII. 1883. Heft II.] 299 



A Singular north- american fly 



{Opsebius pterodontinus n. sp.). 

 C. R. Osten Sachen. 



AmoDg a lot of diptera, collected by the late J. BoU, and which 

 I acquired in Geneva some time ago, I found an interesting Cyrtid, 

 with wings of a peculiar shape, not nnlike Pterodontia. Upon exa- 

 mination, I found that the species belonged to the genus Opsebius Costa 

 (Pithogaster Loew) of which four european and as raany north-american 

 species are already described, but none with that extraordinary deve- 

 lopment of the wings. — (Compare my Catal. N. Am. Dipt. 1878, 

 p. 240.) This character however is merely specific and perhap^ only 

 sexual; the generic characters of the species agree most intimately with 

 those of some other described species of that genus. 



Opsebius pterodontinus n. sp. $ Brownish-hlach, shi- 

 ning, clotlied with dense, erect, fulvous hairs; legs yellow; wings 

 hyaline; costa with a conspicuous , abrupt projection at the end 

 of the ßrst vein. — Length 7 mm. 



The dense hair on the eyes is brownish- fulvous; antennae brown, 

 arista brownish-yellow ; thorax and abdomen are clothed with a uniform 

 covering of erect, fulvous hairs, through which the shining, apparently 

 dark brown, ground color is visible, Halteres whitish- yellow; tegulae 

 transparent, with a yellowish tinge. Legs yellow, with golden-yellow 

 pile; tarsi paler. Wings hyaline, with a slight yellowish tinge; veins 

 yellow; anal cell open; third posterior cell much shorter than the fourth; 

 all the veins reach the margin; fii-st posterior cell divided by a cross- 

 vein, which is a little beyond the discal cell; posterior crossvein nearly 

 opposite (a trifle beyond) the origin of the second vein ; tip of the 

 second vein opposite the proximal end of the second submarginal cell; 

 the costa, soon beyond the ending of the auxiliary vein is thickened, 

 and the tickening forms an abrupt projection, blunt at the tip; the 

 terminal portion of the first vein, likewise conspicuously thickened, runs 



