PROC. EXT. s'dC. WASH., VOL. 20, XO. i>, JUNE, 1918 127 



THE GENUS GNEMEDON EGGER IN NORTH AMERICA 

 iDIPTERA SYRPHIDAE.) 



.1. II. MALLOCH, 

 / r rbana, III . 







The genus Cnemedon was erected by Egger for the reception of 

 two European species and subsequently two others were added. 

 The only distinguishing characters cited are the spurred hind 

 trochanters, and the presence of a very noticeable constriction 

 between posterior margin of apical abdominal segment and 

 hypopygium in the males. The females have not been satis- 

 factorily differentiated. There is one described North American 

 species of the genus, but owing to the doubtful status of Cnemedon 

 it has been retained in Pipizn in which Loew originally described 

 it. An examination of a series of 9 males of this species and 2 

 of another, described herewith leads me to conclude that it is 

 possible to separate the genus Cnemedon from Pipiza by the fact 

 that the latter has a numJDer of hairs on the inner side of hind coxae 

 while the former has not. 



I have no females of either species of Cnemedon so cannot say 

 whether the character will hold in that sex but believe that it 

 will, judging from other genera. 



The two species occurring in North America may be separated 



as follows : 







Hind trochanter with a boot-shaped spur; disc of apical ventral ab- 

 dominal segment flat, frontal and facial hairs almost entirely black ; 

 upper portion of frontal triangle opaque .c.crlcarata Loew 



Hind trochanter with a thumb-like spur: disc of apical ventral ab- 

 dominal segment with 2 small protuberances, a sharp one in center 

 at base and a rounded one in center near apex; frontal hairs largely, 

 facial hairs entirely white; frontal triangle entirely glossy. . . . 

 trochanter at a sp. n. 



Cnemedon trochanteratus sp. n. 



Male. Black shining. I'nder half of third antcnnal joint, arista, 

 extreme apices of femora, bases of tibiae, ami t.he tarsi reddish yellow. 

 Wings clear. Knobs of halteres yellow. Hairs pale, only a few of those 

 on frons black. 



E3 r es long-haired, HoseM. contiguous for a length about equal '< ocellar 

 triangle; arista slightly longer than third aiilennal joint, (he laMer 1 . f> 

 as long as wide. Mid tibia with a less conspicuous ridge on anterior side 

 than in calcerata, and the spur on anterior side of mid coxa much smaller 

 than in that species. 



Length, 6.0 mm. 



