INTRODUCTION*. 9 



well out on disc of wing. Eyes in both 



sexes wide apart 19. 



Venation fairly normal (reduced in DOLICHO- 

 PODIDJE) ; at least one obvious cross-vein 

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

 tiguous, approximate, or wide apart 20. 



19. Second and third longitudinal veins long, 



nearly parallel. Wings Idng, 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 stvle dorsal or apical. 

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

 Discal and second basal cells separate (except 

 in a few EMPID^:). 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. hitiss.}. 



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 , 24. 



24. Antennae reduced. Wings with distinct 



parallel veins ; cross-veins often present. 

 Claws simple. Nearly all the species 



parasitic on bats Streblidae. 



Antennae generally more elongate. Wings, 

 when present, with veins crowded together 

 anteriorly; cross-veins short and near base 

 of wing. Claws large. Parasitic on 

 mammals and birds Hippoboscidae. 



