332 The Two-winged Flies 



mimicry (see Chap. XVII). Erax is a genus with many common gray and 

 black species about an inch long, with sharp-pointed tip of the abdomen. 



The third section or group of Brachycerous families includes many 

 families, in all of which the antennae have the first two segments small and 

 the third curiously large and club-like, and usually bearing a single con- 

 spicuous bristle-like hair. The families of this group can be distinguished 

 by the following table: 



A. Antennae composed of three segments, the third usually large and either with or 

 without a bristle or style. 

 B. Empodium pulvilliform, i.e., feet with three little pads instead of two. 



(Snipe-flies.) LEPTID.E (in part). 



BB. Empodium not pulvilliform, i.e., feet with two little pads and a median bristle 

 or nothing. 

 C. Radial vein four-branched. 



D. Second branch of cubital vein extending free to the margin of the 

 wing or coalesced with the first anal vein for a short distance 



(see Fig. 466) (Bee-flies.) BOMBYLIID.E. 



DD. Second branch of cubital vein joining first anal far from the 

 margin of the wing (see fig. 471). 



(Dance-flies.) EMPIDID^E (in part). 

 CC. Radial vein with not more than three branches. 



D. Head with a curving suture immediately above the antennas. 



(House-flies and allies.) MUSCID^. 

 DD. Head without such suture. 



E. Radial vein with a knot-shaped swelling at the point where 

 it forks, with a small cross-vein running back just at or near 

 this swelling (Fig. 474) . . (Long-legged flies.) DOLICHOPODID.E. 

 EE. Wings without such characteristics. 



F. Second branch of cubital vein appearing as a cross- 

 vein or curved back towards the base of the wings 

 (Fig. 479). 



G. Proboscis rudimentary; mouth-opening small; palpi 

 wanting; antennae with dorsal arista. 



(Bot-flies.) CEsTRiD.t. 



GG. Proboscis not rudimentary; palpi present; antennae 

 with terminal style or arista or dorsal arista. 



EMPIDID^: (in part). 



FF. Second branch of cubital vein not appearing like a 

 cross-vein. 

 G. Front with grooves or a depression beneath the 



antennae (Wasp-flies.) CONOPID^:. 



GG. Front convex beneath the antennae; a spurious 

 vein usually present between radius and media 

 (Fig. 479) . . (Flower-flies.) SYRPHID.E. 



The families of flies named in the above key contain many hundreds of 

 species but few of which are at all popularly known. The bot-flies ((Estridae), 

 house-flies, flesh-flies, bluebottles and stable-flies (Muscidae calyptrata), and 



