140 THE CANADIAN ENTOMOLOGIST. 



joint a trifle broader than long. Thorax opaque black, with narrow yellow 

 lateral borders, rather short, sparse, yellowish pilose. Scutellum trans- 

 lu:e!it yellow, with an apparent black in some lights. Abdomen shaped 

 like that o[ F. thoracicus, but a little more elongate, short yellow pilose, first 

 segment black, somewhat shining ; second opaque black, except a com- 

 plete posterior cross band, and with elongate lateral yellow triangles, which 

 reach from the anterior angle to just before the posterior shining band, 

 and the inner angle of which extends towards the middle of the segment 

 about a fourth of its width ; third segment shining, except a large, square, 

 opaque spot with deep indentations on the sides, situated on the anterior 

 part of the segment ; fourth segment with a similar much smaller spot. 

 All the femora black on the basal half, the anterior pair more extensively 

 SD ; tibire yellow, the posterior pair more or less tinged with brown at 

 the base and apex, posterior tarsi black. Posterior femora considerably 

 thickened with short spinose bristles below, the femora arcuate. Wings 

 hyaline, third vein very deeply bent, marginal cell wide open, last 

 section of the fourth vein straighter than in F. thoracicus^ anterior cross 

 vein in the middle of the discal cell. L., lo mm. 



Described from two female specimens bearing the label " British 

 Columbia." 



The very great differences between this species and the only other 

 described species of the genus F. thoracicus has caused me no little 

 trouble in ascertaining its generic position. The extreme looseness of the 

 definition of the genera of the Syrphidae makes it impossible in many 

 cases to locate a given species in its proper genus, except by a process of 

 finding where better than elsewhere it may be placed. The present is by 

 a great deal the best illustration of this fact that I have so far discovered. 

 Its location in the Eristalini is without any doubt whatever. But as 

 between Triodonta, Teiichoc/iemis, Mallota and Fterallastes, it seems to 

 fit into one about as well as into another. Of these we may more easily 

 throw out of consideration Mallota, on account of the formation of the 

 face and general great pilosity, although the venation is precisely as in 

 that genus. We may next dispose of Teu'chocnemis, in which the third 

 vein is only moderately bent, although we are here approaching differences 

 that are only of specific value. As between Fterallastes and Triodonta, as 

 far as the female sex is concerned, I know of no distinction sufficient to 

 be called generic. In the male sex there are, however, good and sufficient 

 grounds for generic separation. What has led me to place this species in 



