ORDER DIPTERA : THE BRACHYCERA 133 



• 

 {b) The costal vein extends all round the wing ; squamae small ; the 

 3rd antennal segment may have a style or arista or not, or the 

 antenna may consist of a large number of segments LeptiDjE. 

 {c) The costal vein does not reach beyond the tip of the wing 



Stratiomyida and Acanthomerida. 



II. The 3rd antennal segment is simple, not compound, and may have 



a style or arista, or not ; the empodia are pulvilliform : — 



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



and humped ; squamse peculiarly large Acrocerida. 



{b) Squamse small or moderate ; venation of wings peculiarly 



intricate Nemestrinidce. 



{c) Squamse small ; wing-venation more or less like Tabanus 



(Fig. 6) Leptid^. 



III. The 3rd antennal segment is simple, and may have a style or arista, 

 or not ; the empodia, when present, are bristle-like ; the 3rd longi- 

 tudinal vein is forked (and often the 4th also) : — 



(a) Crown of head concave between the eyes : — 



i. The proboscis is a rigid chitinous -dagger ; bristly, hairy 

 flies AsiLID^. 



ii. The proboscis has fleshy labella ; antenna of 4 segments 



Midaida. 



[b) Crown of head not excavated between the eyes : — 



i. Wing with five posterior cells, the 3rd and 4th longitudinal 

 veins curve forwards Apiocerida. 



ii. Wing with five posterior cells, the 4th longitudinal vein does 

 not curve forwards-; predaceous flies THEREVlDiE. 



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 for sucking the 

 nectar from flowers Bombyliidce. 



iv. Wing with three or four posterior cells, anal cell often small ; 

 femora and tibise often with combs of spinules ; smallish 

 dull-coloured predaceous flies usually with a stiff proboscis 

 for impaling prey Empidid^. 



v. Wings with three posterior cells ; proboscis not projecting ; 

 smallish flies usually found on windows Sceno-pinidce; 



IV. The 3rd antennal segment is simple, and may have an arista or not ; 

 the empodia when present are bristle-like ; 3rd longitudinal vein 

 not forked : — 



(a) Wings shaped like a lance-head, the venation somewhat as in 



Psychodidse Lonchopterida. 



(b) Second basal cell confluent with discal cell ; anal cell, if present, 



small ; usually brilliant-coloured flies with metallic sheen 



DOLICHOPODID/E. 



{c) Second basal and discal cells either confluent or distinct ; anal 



cell, if present, small ; not brilliant-coloured flies Empidid^. 



