312 



— Upper pair of cephalic thorns directed forward, at most slightly 



divergent apically, generally slightly curved downward or head 

 without strong upper thorn 10 



10. Head with strong thorns, or if these are absent the abdomen has 



the dorsal transverse armature consisting of very strong thorns 

 and intervening long slender hairs; apices of antennae obtuse. .11 



— Head very rarely with strong thorns, 2 carinate elevations present 



on upper anterior margin ; antennae with apices attenuated ; body 

 without thorns, sometimes with bristles 12 



11. Lower median portion of face with a closely approximated pair of 



stout thorns which are occasionally fused almost to apices ; ab- 

 domen with the transverse armature of the dorsal segments con- 

 sisting of short flattened thorns and long slender hairs, the thorns 

 usually appearing as if attached to rather than forming a part of 

 the abdomen and sometimes turned up at bases and apices 



BOMBYLIIDAE (p. 389) . 



— Lower median portion of face without thorns ; abdomen with the 



transverse armature consisting of alternating long and short 

 thorns except in Leptogaster Asilidae (p. 373). 



12. Cephalic armature consisting of 2 carinated elevations on upper 



anterior margin, on each of which is a very long hair ; antennal 

 sheaths raised above level of face, tapering apically, directed 



downward and slightly outward; proboscis much elongated 



Empididae (p. 400). 



— Similar to foregoing, but with the proboscis short 



DOLICHOPODIDAE (p. 403) . 



IMAGINES 



1. Empodium pulvilliform, nearly or quite as large as the pulvilli, so 



that 3 rounded pads or scales appear under the tarsal claws. . . .2 



— Empodium either absent or in the form of a slender thread, with or 



without surface hairs, so that there are only 2 distinct pads or 

 scales under the tarsal claws 8 



2. Third antennal joint distinctly annulated or the antenna consist- 



ing of more than 3 distinct joints 3 



— Antenna consisting of 3 joints, the third not annulated 6 



3. Costal vein discontinued at or close to the apex of wing 



I Stratiomyiidae* (p. 315) . 



1 ACANTHOMERIDAE (p. 354). 



— Costal vein continued round apex of wing, sometimes encircling the 



whole posterior margin 4 



4. Squamae very large Tabanidae (p. 355) . 



— Squamae small, sometimes vestigial 5 



*The family Acanthomeridae is doubtfully distinct from Stratiomyiidae. I 

 have no species of the former, all occurring in South America. 



