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Transactions. 



or pubescent (hairy in some exotic species). Face of varying shape ; 

 concave (fig. 48), convex, arched (fig. 5), or vertical (fig. 7) below antennae, 

 with (fig. 15) or without (fig. 52) a central tubercle or swelling ; sometimes 

 produced at oral margin (fig. 52) ; clothed with hairs or bare, and some- 

 times transversely wrinkled ; oral margin horizontal, descending (fig. 63) or 

 ascending (fig. 5) ; cheeks more or less well developed and usually clothed 

 with hairs. The proboscis well developed, the label! a larger or smaller ; 

 the palpi slender or stouter. 



Thorax usually robust, sparsely or densely clothed with long or short 

 hairs or with pile, or altogether bare ; scutellum crescentic or quad- 

 rangular, sometimes tuberculate, clothed or bare. Legs well developed, 

 slender or stout, the posterior femora sometimes thickened and with a 

 swelling or a tooth-like process below toward apex or base ; the tibiae 

 and tarsi sometimes broadened and peculiarly developed ; the legs some- 

 times clothed with longer or shorter hairs and less commonly with bristles 

 which are most frequent on underside of the posterior femora, on the tarsi, 

 and abdomen, particularly on the genital segments of the male ; claws and 

 pulvilli small or well developed, the empodium bristle-like or styliform. 



The wings usually longer than the abdomen, in some cases shorter ; 

 incumbent when at rest or held slightly divergent just exposing the 

 abdomen. The wings vary somewhat in outline, being apically pointed 



IstA'+Cug Cu,+M 3 2ndM 2 M 1+2 



Fig. 1. — Diagram of a syrphid wing, showing venation. 



or blunt, while the anal angle is evenly rounded or strongly developed ; 

 the alula is usually short, but may be long and narrow, reaching almost 

 to the posterior margin of the wing (fig. 2) ; the squamae and anti- 

 squamae are well developed and fringed with hairs, those on the former 

 being long and frequently branched, and on the latter short. In colour 

 the wings are either clear or tinged over the whole or part of the mem- 

 brane, the base and cell Sc being more deeply coloured. The venation 

 (fig. 1), which is distinct and readily characterizes the family, presents 

 Rome interesting peculiarities. The costa ends at its junction with vein 

 R 4 + 5 either at or before the apex of the wing; sometimes there is a 

 supernumerary humeral vein present ; in some cases Sc 2 is developed, 

 uniting as a cross- vein, Scj with R x near the apex of the former ; vein 

 R 2 + 3 runs more or less straight, or is strongly curved upward and 

 sometimes slightly backward at its apex to meet the costa or to unite 

 with vein R l5 thus closing cell B, 1 ; vein R 4 + 5 is straight, slightly curved 

 downward, or deeply looped into cell R 5 , which is always closed apically 

 either on, near, or considerably before the costa by the confluence of 



