32 OHIO BIOLOGICAL SURVEY 



nearly always present and characteristic of the family. The post-alar 

 membrane, or squamae, with peculiarh^- formed, forked, and fan-like cilia- 

 tion; and the plumula (an elongated, fringed, filament-like projection 

 from the upper margin of the pteropleurae beneath the squamae ) are 

 peculiar to the Syrphidae. 



The mouth-parts of the adults (vSee Plate VIII, Figs. 153-7) ^^ ^^ot 

 seem particularly well adapted either for lapping up nectar or for the 

 prehension or ingestion of pollen grains. The labrum-hypopharynx is 

 somewhat lancet-like as though it might serve for piercing plant or an- 

 imal tissues (See Fig. 156). But such a habit is known at the most for 

 onl}^ a single species (See p. 35); while an examination of stomach con- 

 tents has indicated hone}' and pollen-grains in abundance. The oral 

 opening is large, the proboscis usually short and, when at rest concealed 

 within the mouth. The maxillae (Plate VIII, Fig. 154) show a blade- 

 like maxillary lobe and bear a somewhat flexuous, one-jointed palpus. 

 The labium is short, cylindrical, unfolding in a hinge-like manner, ex- 

 panded at the tip into a bilobed labellum or lapping tongue provided with 

 tracheae (Plate VIII, Fig. 153). The whole acts like a sponge, the nectar 

 rising by capillar}^ attraction. The antennae of the adults bear remark- 

 ably complex and S57mmetrical olfactory pits indicating that this sense is 

 well developed. These pits (See Plate VIII, Fig. 160, 161) are open and 

 their walls are lined by a large number of olfactory pegs or perceptory 

 end organs which send nerve fibres in to the central ganglia. 



While the colors are various, the species of this family are charac- 

 teristically marked with j^ellow, in spots, bands, or stripes, on head or 

 thorax, but particularly on the abdomen. Many of them resemble 

 Hyme7ioptera and are to be found about flowers, hovering in the air like 

 hummingbirds, or crawling about over the blossoms in search of nectar 

 and pollen. 



The one character by which anyone can distinguish Syrphidae from 

 all other flies is the so-called "false or spurious vein" which is a thread- 

 like thickening of the wing- membrane, between the third and fourth 

 longitudinal veins and running thru the anterior cross-vein, (Plate VIII, 

 Fig. 151 j. It has the general apperance of a vein but is not so clear- 

 cut nor so deep in color and its outer end, at least, is free. It is present 

 in all but a very few Syrphidae and not found in the members of any 

 other family. 



Secondary .sexual characters occur on head, legs and abdomen, and 

 are absent from the thorax and wing. None of them seem to be charac- 

 teristic of this family. Many are of u.se as generic characters. 



