INTRODUCTION. 



9 



well out on disc of wing. Eyes in both 



sexes wide apart 19. 



Venation fairly normal (reduced in Dolicho- 

 podid^) ; at least one obvious cross-vein 

 well out on disc of wing. Eyes in $ con- 

 tiguous, approximate, or wide apart 20. 



19. Second and third longitudinal veins long, 



nearly parallel. Wings long, tips pointed ; 

 venation different in the sexes ; no wing- 

 less species Lonchopteridae, 



Second and third veins united in one rather [p. 387. 



short strong vein. Wings short, tips well 

 rounded ; venation similar in both sexes ; 

 some species wingless Phoridae. 



20. Discal cell united to 2nd basal cell ; basal 



cells very short or obsolete. Third longi- 

 tudinal vein diverging from a swelling 

 near base of wing; anterior cross-vein at 

 same spot; third vein never forked. Pro- 

 boscis soft. Arista or style dorsal or apical. 

 Abdomen normally 5- or 6-segmented. .. . Dolichopodide. 

 Discal and second basal cells separate (except 

 in a few EMPiDiE). Basal cells generally 

 long enough to be obvious. Second and 

 third veins diverging well away from base 

 of wing ; third vein not forked, except in 

 some Empidje. Proboscis rigid or soft . . 21. 



21. Antennal style present or absent ; arista, if 



present, generally dorsal. Proboscis gene- 

 rally rigid, pointed. Abdomen normally 

 7- segmented. Second and third longi- 

 tudinal veins diverging at one-third of the 



wing; third vein often forked . Empidae, p. 321. 



Antennal style never present; arista, when 

 present, nearly always dorsal. Third vein 

 never forked 22. 



22. Proboscis rudimentary; palpi rudimentary or 



absent. In larval stage always parasitic 



on mammalia CEstridae. 



Proboscis and palpi always distinctly pre- 

 sent. In larval stage rarely parasitic on 

 mammalia Muscidae (s. latiss.). 



23. Head folding back on dorsum of thorax. 



Wingless species. Parasitic on bats .... Nycteribiidae. 

 Head not folding back on thorax. Winged 

 or wingless species. Parasitic on birds and 

 mammals c . . , 24. 



24. Antennas reduced. Wings with distinct 



parallel veins ; cross-veins often present. 

 Claws simple. Nearly all the species 



parasitic on bats Streblidae. 



Antennas generally more elongate. Wings, 

 when present, with veins crowded together 

 anteriorly ; cross-veins short and near base 

 of Aving. CJlaws large. Parasitic on 

 mammals and birds Hippoboscidas. 



