58 Syrphidae. 



the hind margin of tiie fourth segment and tiie side elevations shining; 

 in the middle it is clothed with short, black hairs, but all the sides 

 and the side elevations have long pale to whitish hairs, almost pre- 



Fig. 17. Antenna of P. dubium cf, from the inside. X 80. 



dominant on the second segment, and longest at the basal corners. 

 Venter blackish, shining, a little translucent; it has long more or less 

 pale hairs, most dense and dark on the fourth segment. The genitalia 

 forming a somewhat large knob, and reaching rather long in under 

 the venter. Legs black, anterior knees yellov^r, sometimes somewhat 

 broadly, hind knees narrowly yellow, and the middle metatarsus yel- 

 low except the apex; hind metatarsus slightly thickened. The legs 

 haired as usual, the hairs on femora rather long, yellowish or darker 



Fig. 18. Wing of P. dubium d". 



to blackish and darkest on the front femora and above the hind 

 femora; tibiæ black-haired, the hairs long above the hind tibiæ and 

 here sometimes W\i\\ a few pale intermingled ; also above the anterior 

 tibiæ the hairs somewhat long; below the apical part of front and 

 hind tibiæ and the first tarsal joints there is the usual, adpressed, 

 yellow pubescence; tarsi with longer hairs above than in Cnemodon. 

 Wings hyaline or a little tinged about the middle; stigma dirty yel- 

 lowish; the upper marginal cross-vein about as in P. Hermgi, but the 

 bend less angular or more roundly curved, the upper angle acute. 

 Squamulæ smoky or blackish with a darker margin and a yellowish 



