SYNOPSIS OF NORTH AMERICAN SYRPHID.^. XXIII 



present without the antennal character— for these Atemnocera is pro- 

 posed. But to be coiisisteut yet another divisiou shouhl be created for 

 the excised antenme without the scutellar bristles, as in Volucella 

 megacephala. Even such a dismemberment of the genus might be well, 

 were it natural, but it is not ; allied species are torn asunder and unre- 

 lated ones are thrown together. A natural classification, moreover, 

 would require the same treatment of Phalacromyia. 



SERIC03IYINI. 



Large s^yecies ; antennce short, the third joint scarcely longer than broad; 

 arista basal, plumose ; anterior cross-vein of wings oblique, near the mid- 

 dle of discal cell ; hind femora sometimes thickened. 



a. Moderately pilose ; abdomen with yellow interrupted cross-bands 



Sericomyia Meig. 



aa. Thickly pilose, abdomen uniformly black Arctophila Schiner. 



This group at present is limited without much difficulty. Still the 

 forms are not very closely allied in some of their species. The con- 

 nection between the two genera is found in 8. militaris. In Arctophila 

 flagrans the thickened hind femora and curved third longitudinal vein 

 present a relationship with the next group. 



ERISTAIilNI. 



Mostly large, pilose species, uniform in color, or more or less variegated; 

 third joi tit of the antennce short, oval or transverse; third longitudinal 

 vein with a deep concavity into the first posterior cell; anterior cross-vein 

 near or beyond the middle of the discal cell; hind femora thickened, except 

 in species of Eristalis. 



a. Marginal cell closed and petiolate. 

 1). Thorax never with yellow markings. 



c. Frontal triangle of male strongly protuberant Doliosyrphus Bigot. 



cc. Front evenly arched Eristalis Latr. 



&6. Thorax with yellow spots. 



d. Hind femora without a conical projection below, near the end, 



Pteroptila Loew. 

 dd. Hind femora with a projection below {Milesia). 

 aa. Marginal cell open. 



e. Arista plumose {Sericomyini). 

 ee. Arista bare. 



/. Face with a longitudinal ridge in the middle ; hind femora strongly thickened, 



and with an angular protuberance below Tropidia Meigen. 



ff. Face not distinctly carinate ; tuberculate or rounded. 

 g. Thorax and scutellum not densely pollinose above. 



h. Third joint of antenme oval ; dorsum of thorax usually with distinct stripes, 



Helophilus Meigen. 

 hh. Third joint of anteunaj ^iroad ; throax not vittate. 



i. Thickly pilose Mallota Meigen. 



a. Thinly pilose Triodonta Will. 



Teuchocxemis O. S. 

 gg. Thorax and scutellum very densely pollinose above Pteraxlastes Loew. 



