AMERICAN DIPTERA. 267 



Cyrtopogon marginalis. 



Cyrtopogon marginalis Loew, Cent., VII, 60, 1866. 



Cyrtopogon marginalis Loew, Berl. Ent. Zeit., 1874, 365, note. 

 % <?. — Length 10-12 mm. — Black; antenna?, except at base and tip, 

 reddish-yellow; apex of the femora, tibiae and tarsi reddish; thoracic 

 dorsum brownish pruinose, broadly polished black above the dorso- 

 pleural suture; segments 2—5 of abdomen each with an interrupted 

 white pruinose fascia; wing, excepting grayish tip, hyaline. 



Black; face, front and occiput thinly grayish pruinose, the face 

 more thickly so. First two segments of the antennas black, apex of 

 the second and third segment reddish-yellow, extreme apex of the 

 latter and the style blackish. Pile on the middle of the face, first two 

 antennal segments, ocellar tubercle and occiput below fine and white; 

 that edging the mystax on the sides, on the oral margin, frontal orbits 

 and upper occiput black. Dorsum grayish or brownish pruinose; the 

 usual geminate and broader lateral stripes darker; subobsolete, while 

 the shade of the bloom is always in sharp contrast with the rather 

 broad polished black band that extends from, and including, the 

 humeri backward above the dorso-pleural suture to the scutellum; 

 pile on the polished area black; on rest of dorsum short and white. 

 Pleura? glayish- white pruinose with a bare polished area in the middle; 

 pile of the mesopleura, sternopleura and before the halteres unusually 

 long, furry, white. Scutellum polished black; white pilose. Abdomen 

 polished black; segments 2-5 each with an interrupted white pruinose 

 fascia on its posterior portion, not touching, however, the extreme 

 posterior margin except on the sides. Posterior margins of the seg- 

 ments and the venter white pilose; rest of abdomen black pilose; the 

 black pile of the male is much longer and more pronounced upon the 

 sides, where, when viewed from before, it forms a distinct tuft upon 

 segments 2-4. Femora black, reddish at base and tip, with long 

 white pile, below rather yellowish; on the extreme apex black. Tibia? 

 reddish, darker toward the tip; black pilose on the inner, white pilose 

 on the outer side. Tarsi likewise reddish, darker in the female, the 

 first segment verging toward yellow; the front tarsi of the male more 

 slender and wholly bright yellow, with pile and bristles of same color; 

 bristles of the remaining tarsi and of the tibiae black. Wings hyaline, 

 veins yellow toward base, the marginal and first submarginal cells 

 toward their apices and the second submarginal cell entire grayish. 



Type. — M. C. Z. Five females and one male; one female 

 of which only is probably the type. I have made one male 

 and two female homotypes, which are deposited one each in 

 the collection of the Massachusetts Agric. College, Am. Ent. 

 Soc. of Phila. and in my own private /collection, respectively. 



Habitat.— Canada; White Mts., N. H. ; Springfield, Mass. 



TRANS. AM. ENT. SOC, XXXV. JULY, 1909 



