92 NORTH AMERICAN DIPTERA. 



About forty species of this family are known from North 

 America. They are all flower-flies, not very quick in flight. 

 Flies of some of the genera (Conops, Physocephala and Tropido- 

 myia) have a curious resemblance to certain wasps, and yet 

 more to the species of Ceria among the Syrphidae. The genus 

 Stylogaster is remarkable for the very long ovipositor of the 

 female and the elongate proboscis in both sexes. The four 

 known species are from Africa, North and South America. 



So far as known, the larvse of this family are parasitic upon 

 adult hymenoptera (wasps and humble-bees) and orthoptera.. 

 The eggs of the female are laid directly upon the bodies of 

 the bees or wasps during flight. The young larvse burrow 

 within the abdominal cavity of their host, and there remain, 

 the posterior end directed toward the base of the abdomen, 

 feeding upon the non-vital portions, until ready to transform 

 into the mature fly, when they escape from between the 

 abdominal rings of the insect. The larvse of Conopidae 

 are oval or pear-shaped, with distinctly differentiated seg- 

 ments, which are capable of extension or contraction. The 

 antennas are wart-like, with two chitinous, ocellus-like rings at 

 the extremity. The mouth-hooklets are strongly bent. On 

 the last segment there are two, large, round or kidney-shaped 

 stigmatic plates, arched like a watch crystal. The puparium 

 is oval, with button-like, slightly projecting anterior stigmata 

 and the posterior pair as in the larvse. They remain within 

 the body of their host during the winter. 



TABLE OF GENERA. 



1. Antennas with a terminal style; proboscis directed forward, without me- 



dian hinge ; abdomen constricted toward the base. . . 2 

 Antennae with a dorsal or subdorsal arista 4 



2. Face witli a median ridge, without ^-shaped grooves (Central and South 



America.) ....'... TKOPIDOMYIA Williston. 

 Face with a well-marked ^-shaped groove > 



3. Femora and tibiae not thickened or dilated, or, if so, the thickening reg- 



ular ; small cross-vein of the wings nearly opposite 'the tip of the 

 auxiliary vein, and near the middle of the discal cell. Coxois Linne. 



