XIII] SYNOPSIS OF FAMILIES 225 



Synopsis of the families of Orthorrhapha Brachycera 1 . 



I. Third antennal segment composed of a series of in- 

 distinctly separated subsegments ; empodia pulvilliform ; third 

 and fourth longitudinal veins forked. 



(a) Costal vein extending all round the wing ; squamae large ; the third 

 antennal segment never has a style or arista . . . . Tabanida. 



(b) Costal vein extending all round the wing ; squamae small ; third 

 antennal segment may have a style, or arista, or not, or the antenna may 

 consist of a large number of segments . . . . . . . . Leptidts. 



(c) Costal vein not extending beyond tip of wing, longitudinal veins not 

 crowded anteriorly ; two sub-marginal and five posterior cells always present, 

 the fourth closed. Third antennal joint composed of seven annuli, with a 

 terminal style or arista . . . . . . . . . . Acanthomeridcs. 



(d) Costal vein not extending beyond tip of wing ; longitudinal veins 

 usually more or less crowded anteriorly, posterior ones often weak ; four or 

 five posterior cells, the fourth rarely or never closed . . Stratiomyidcs . 



II. Third antennal segment simple, with or without a 

 terminal style or arista ; empodia pulvilliform. 



(a) Head small, formed almost entirely by the eyes ; thorax large and 

 humped ; squamae peculiarly large . . . . . . . . Acrocerida. 



(b) Squamae small or moderate ; venation of wings peculiarly intricate 



Nemestri nidcs . 



(c) Squamae small ; wing venation more or less resembling that of 

 Tabanus . . . . . . . . . . . . . . . . Leptidce. 



III. Third antennal segment simple, with or without a 

 terminal style or arista ; empodia, when present, bristle-like ; 

 third longitudinal vein, and often the fourth, forked. 



(a) Crown of head concave between the eyes : 



(i) Proboscis a rigid chitinous dagger ; flies bristly and hairy 



AsilidcB. 



(ii) Proboscis with fleshy labella ; antennae composed of four segments ; 

 flies without bristles . . . . . . . . .... * Mydaides. 



(b) Crown of head not excavated between the eyes : 



(i) Wing with five posterior cells ; third and fourth longitudinal 

 veins curve forwards . . . . . . . . . . . . Apioceridce. 



(ii) Wing with five posterior cells ; fourth longitudinal vein does not 

 curve forwards ; predaceous flies . . . . . . Thevevidce. 



(iii) Wing with three or four (rarely five) posterior cells and often 

 with dark markings ; anal cell large ; usually hairy bee-like flies, often with 

 a long slender proboscis used for sucking the nectar from flowers Bombyliidce. 



1 Modified from Alcock, loc. cit. p. 132. 

 H. B.F. 15 



