82 NORTH AMERICAN DIPTERA. 



CYCLORRHAPHA. 



28. SYRPHIM:. 



Small to rather large flies. Head hemispherical, often elon- 

 gated or produced in the lower part; as broad or a little broader 

 than the thorax. Face moderately broad, bare or clothed with 

 dust or short pile; excavated in profile under the antennae 

 and projecting below, or with a distinct convexity near the 

 middle part, never with longitudinal furrows or lateral ridges, 

 usually convex transversely, sometimes with a median ridge. 

 Oral opening large ; proboscis rarely much elongated. Front 

 never excavated. Antennas usually porrect and approximated 

 at their base, three-jointed, usually with a dorsal arista. 

 Eyes large, bare or pilose ; in the male usually contiguous 

 above. Ocelli always present. Thorax comparatively large 

 and robust, moderately arched above. Tegulse of moderate 

 size. Abdomen composed of five or six visible segments, rarely 

 with only four. Hypopygium usually not prominent. Legs 

 usually of moderate strength. Macrochsetae rarely present in 

 any part of the body ; the body generally thinly pilose or bare, 

 but sometimes clothed with thick pile. Wings comparatively 

 large ; third longitudinal vein never forked ; marginal cell 

 open or closed ; the fourth vein terminates in the third at or 

 before the tip ; three posterior cells ; basal cells large ; anal 

 cell always closed before the border of the wing ; between the 

 third and fourth longitudinal vein and nearly parallel with 

 them, a false or spurious vein, nearly always present and 

 characteristic of the family. 



The family Syrphidse is one of the most extensive in the 

 order. Nearly twenty -five hundred species are known through- 

 out the world and many new forms are constantly being added. 

 They contain among them many of the brightest-colored flies, 



