SYRPHIDiE. 235 



alulae, lanuginose. Wings incumbent or divaricated in repose ; hind 

 margin veinless, the costal vein ending at or before the tip of the wing, 

 where it receives the cubital, or radial in case the cubital is previously 

 merged in this {VoluceUa, EristaUs) ; mediastinal vein distinct, ending 

 about the middle of costa, subcostal continued nearer to the tip ; me- 

 diastinal areolet (contained between the two) often coloured, appearing 

 as a narrow stigma ; tcrnate areolet long, viz., the prtebrachial extend- 

 ing to about the half-length of the wmg, the pobracliial not much shorter, 

 the aual again longer, tapering to a ])oint nearly at the hind margin ; 

 discal approaching tlie liind margin ; a transverse vein connecting the 

 cubital with the praibrachial vein near the margin, forming a complete 

 sul)apical areolet, often like the discal in size and shape, rarely divided 

 into two by another transverse vein about the middle {Microdon) ; ex- 

 terno-niedial veins not quite reaching the margin. Two spurious veins, 

 one before the praebrachial, another behind the pobracliial. The lon- 

 gitudinal creases of the Aving are particularly strong in this family, the 

 elevations being crowned by the subcostal, the first spurious, the pobra- 

 cliial veins, and the axillary axis, respectively. Axillary lobe usually 

 ample and rounded, rarely indistinct (see table of genera). Alulae mo- 

 derately large, rarely so large as to cover the halteres (EristaUs), or very 

 small {Baccl/a, &c.). Abdomen seldom showing more than five seg- 

 ments externally, the first short, but complete below as well as above ; 

 the sides sometimes margined ; the sexual appendages not very obvious : 

 the abdomen is often nearly filled with air, and-- partly diaphanous. 

 Legs of moderate length ; fore pair distant from the intermediate, and the 

 coxcG not so long as to reach these; iiiud femora sometimes enlarged, 

 and toothed or spined; tibia? without terminal spurs, posterior pairs 

 rarely with a few bristles at the sides (Ckri/soclamis); tarsi with the first 

 joint sometimes enlarged ; onychia broad, membranous, hairy beneath ; 

 empodium recurved, slender, pointed, pubescent. 



The coalescence of the palpi with the maxillse, and the marked 

 spurious veinsj are characters almost peculiar to this family. They 

 differ besides, from the Plafj/pezicke bv the length of the ternate 

 areolets, and the closed subapical areolet, — from Pipmictilida; by 

 the same characters in a less degree, and also by the ample face, — 

 from Conopidce by the long pobrachial areolet, — from the " calyp- 

 trate " Muscidce by the length of the anal also. 



The flies of this family are not predaceous, feeding mostly on 

 the nectar of flowers. They love to hover in the air over one 

 spot, their wings almost invisible through the rapidity of their 

 vibration, accompanied with a shrill hum ; if alarmed they dart 

 away with astonishing velocity, but soon resume a similar station. 

 The larvae are among those with a flexible head (" leech-like," 

 Bouche), usually broad behind, attenuated before, otherwise vary- 

 ing much in figure, as they do in their food and habitation. The 



