AET. 9 AMERICAN XYLOTINE SYRPHID-FLIES SHANNON 7 



Lower face. — The region between the lower margin of the eye and 

 the lateral mouth margin. 



Apical cross vein. — That part of the third vein beyond the point 

 of juncture of the posterior cross vein and the fourth vein. It may 

 be in line with the posterior cross vein or it may have a basal angle 

 which throws it out of alignment with the posterior cross vein. 



KEY TO THE GENERA OF NORTH AMERICAN XYLOTINI 



A\ Sixth vein, beyond anal cell, evanescent some distance from wing margin ; 

 stigmatical cross vein fairly distinct ; metasteruum pilose—Teuchocnemis. 

 A^ Sixth vein attaining wing margin. 



B". Mesonotal tegument ochraceous ; stigmatical cross vein present ; meta- 

 stemum bare; length of petiole beyond anal cell a little longer than 



discal cross vein Pterallastes. 



B". Mesonotal tegument not ochraceous ; stigmatical cross vein absent ; anal 



cell petiole shorter than discal cross vein. 



C\ Metasternum pilose; hind trochanters of male not spurred (except 



rarely in Tropidia). 



D\ Hind femur on outer side with an apical saw-toothed process; 



each meta sternal sclerite divided by a membranous band ; fifth 



tergite of female small, membranized and nearly hidden under 



fourth tei'gite; face subcarinate to carinate Tropidia. 



D^ Hind femur vpithout saw-tooth process, etc. 



E\ Face subcarinate ; sternites very narrow ; hind femur greatly 



enlarged ; anal furrow usually much shortened ; pleuroter- 



gite with sharp ridge ; ocellar triangle of male unusually 



long and narrow. 



F\ Wings nearly devoid of villi, glassy in appearance ; arista 



shorter than width of face Syritta. 



F^ Wings villose, not glassy; arista distinctly longer than 



width of face (Tropical) Planes. 



E^ Face without any semblance of carina ; sternites not un- 

 usually narrow ; anal furrow not shortened ; pleuroterglte 

 without ridge ; ocellar triangle of male normal. 

 F\ Head broadly elliptical; body pile inconspicuous (Xylota, 

 in part, tj'pe Xylota vecors Osten Sacken)_Xylotomiina. 

 F". Head triangular ; pile usually fairly long and leather 

 dense (Brachypalpus, in part, type inarmatus Hunter) 



Xylotodes. 



C^ Metasternum faintly pubescent or bare (hind trochanters of male 



spurred in Xylotodes and Xylota except in X. Mcolor). 



D\ Not bumble-bee-like; without contrasting yellow and black 



mesonotal pile. 



E^. Abdomen and sometimes the thorax bright brassy aeneous ; 



face largely yellowish Calliprobola. 



E^ Abdomen not bright brassy aeneous ; face rarely with yellow. 

 F\ Head triangular ; arista much shorter than width of face ; 

 metathoracic spiracle distinctly smaller than third 

 antennal joint ; hind femur swollen and with obtuse 

 spur apically and ventrally ; front of female broad. 

 {Brachypalpus, sensu stricto) Brachypalpus. 



