203 

 Family Cyrtidae 



Opsebius pterodontinus. 



Small to moderately large flies, never elonoate, pilose or nearly bai'e. 



Head small to very small, composed chiefly of the compound eyes 

 which are usually contiguous in both sexes, the front, face or both 

 obliterated; none, two or three ocelli present. Antenna? composed of 

 two or three segments, with or without an apical arista, the third seg- 

 ment sometimes with apical bristles. Proboscis rudimentary or long, 

 sometimes greatly exceeding the length of the body. Thorax large 

 and convex, the sciuamge and scutellum large. Abdomen inflated, convex, 

 rather orbicular. Legs moderately stout, the empodia and pulvilli pad- 

 like. Venation variable, the veins sometimes weak and indistinct; often 

 a supernumerary crossvein between the third and fourth veins. 



This family contains a small number of species and may be recog- 

 nized by the swollen thorax, inflated abdomen and small head. Ten 

 genera are known to occur in North America. Cole* has revised the 

 family. Insofar as known tlie members of the family are parasitic on 

 spiders. 



KEY TO GENERA 



1. Prothoracic lobes j2:reatly enlarp;e(l and meeting in front of the mesono- 



tum; proboscis elongate (3, 4) Philopota Wiedemann 



Prothoracic lobes not forming a shield in front of the mesonotum... 2 



2. Proboscis small and aborted 4 



Proboscis elongate 3 



3. Palpi absent; usually two ocelli (13, 14) Lasia Wiedemann 



Palpi present; three ocelli situated on a moi-e or less prominent 



tubercle (11, 12) Eulonchus Gerstaecker 



* 1919. Trans. Amer. Ent. Soc, xlv. pp. 1-79, plates I-XV. • 



