Knab — On Some North American Species of Microdon. 137 



pair of indistinct narrow blackish longitudinal stripes ; pile dirty yellow- 

 ish gray, short and dense, longer and paler at lateral margins. Scutellum 

 deep blue, broad and short, strongly convex, the hind margin rounded 

 and with only a slight trace of median emargination, the spines rather 

 small and remote from each other; pile yellow-gray, long and dense. 

 Abdomen large, elongate-ovate, much broader than the thorax, broadest 

 at hind angles of second segment and beyond this rounded off to the blunt 

 apex; dorsum flattened anteriorly, convex on distal half; vestiture on 

 second and third segments of creamy white pile, dense and longer at the 

 sides, on the second covering the entire dorsum, on the third the sides 

 and forming a broadly interrupted apical band; distal portion of abdo- 

 men with sparse and inconspicuous dark hairs. Legs black, the tibiae 

 basally tinged with dull ferruginous ; vestiture short and inconspicuous, 

 that on the femora black, that on the tibiae with creamy yellow luster; 

 tarsi ventrally with ferruginous yellow cushions ; pulvilli ferruginous, 

 with a fine white fringe. Wings moderately broad, tinged with gray, 

 without distinct cloudings at the cross-veins; posterior angles of first 

 posterior and discal cells roundedly produced, not appendiculate, a large 

 spur projecting into middle of first posterior cell from third vein. Halteres 

 yellowish. Length: Body about 12 mm., wing 9 mm. 



Female. — Frons at posterior angles of eyes about one-third the width 

 of head, the eye-margins straight and diverging very gradually to lower 

 part of face ; transverse furrow indistinct. Vestiture of mesonotum and 

 scutellum much more dense than in the male. Wings on distal half with 

 brown cloudings along the veins. Abdomen broader than in the male, 

 more strongly tapered toward the tip. Length: Body about 13 mm., 

 wing 10 mm. 



Seattle, Washington, one male, issued June 27, 1901 (C. V. Piper) ; 

 Oregon, one female, without indication of exact locality or collector; 

 Mount Hood, Oregon, one female (Williston collection). 



Type: Cat. no. 21,414, U. S. Nat. Mus. 



The female from Mount Hood was included by Williston under cothur- 

 natus in his "Synopsis of North American Syrphidse," page 8; it is in a 

 poor state of preservation. The male was reared by Prof. C. V. Piper. 

 The puparium resembles that of cothurnatus , showing reticulations of a 

 very similar character ; these differ, however, in being more uniform, 

 without the differentiated median and lateral series observable in cothur- 

 natus ; it is also slightly less convex. 



Microdon bombiformis Townsend. 



There are seventeen specimens of this very distinct species before me, 

 one from AVashington, District of Columbia, without indication of col- 

 lector, four taken in Rock Creek Park, District of Columbia, by C. H. T. 

 Townsend, the other twelve taken at Inglenook, Pennsylvania, by Mr. 

 Daecke. Johnson has recently recorded the occurrence of this species in 

 Massachusetts and Connecticut (Psyche, vol. 23, 1916, p. 76). 



The series of both sexes before me is remarkably uniform in coloration. 



