1917] New Species of Colorado Syrphidce 227 



the apex of the anterior femora have stout black pile, and in 

 that the posterior cross-vein is about two-thirds of the penulti- 

 mate sections of the fourth vein, instead of being equal. 



B. riifiahdominalis differs from B. vacua in the color of the 

 thorax and its markings. B. vacua has three brown stripes and 

 B. rufiabdommalis has four, two entire and two interrupted. 

 B. vacua is 8-9 mm. and B. rufiabdominalis is 7 mm. 



B. rufiabdominalis differs from B. bicolor Fallen, of Europe, 

 in that the occiput of the latter is pale gray and with gray pile, 

 the face is without pubescence, the eyes touch for about one- 

 third of the distance from the ocelli to the antennae ; the scutellum 

 has eight long black marginal hairs and is covered with short 

 black pile, while in the former the occiput is black, whitish- 

 pollinose and has black and white pile ; the face has fine whitish 

 pubescence on it; the eyes are distinctly separated, the nearest 

 point of contingency is immediately below the ocelli; the 

 scutellum has black pile dorsally, and the remainder is covered 

 with reddish pile and lacks the eight black marginal bristles. 



Volucella rufomaculata n. sp. 



Length, 9 14 mm., cf 15 mm. Face yellowish chestnut, thickly 

 clothed with a medium long, yellow pile; separated in both sexes by a 

 narrow yellowish strip. Considerably excavated and bare below the 

 antennae. Cheeks shining black, black pilose, in the female with a small 

 yellow triangular spot near the eye; in the male this spot connects with 

 the narrow yellow stripe next to the eye. Antennae reddish brown, 

 lighter at tip, third joint elongate, widest at the base. Arista more than 

 twice as long as the antenna, reddish, with long abundant feathery, 

 black plume; front of the female distinctly yellow, rather narrow, 

 converging at the apex with abundant long, yellow pile. Front of the 

 male brown, shining, sparsely covered with whitish pile, frontal triangle 

 of the male very small, yellow, with abundant long, yellow pile. Eyes 

 of the female sparsely pilose throughout, in the male thickly pilose. 

 Dorsum of thorax, bright shining blue with moderately long black pile. 

 Anterior, lateral margins, posterior margin and pleura with abundant 

 long, yellow pile. vScutellum light-yellow with abundant long, yellow 

 pile. Abdomen shining black with yellow pile, more abundant on 

 lateral margins of second and fourth segments. First segment black, 

 shining, second segment with a pair of large, yellow lateral triangular 

 spots connected on posterior margin with a reddish band, pile of the 

 sides abundant, in the middle sparsely pilose. Third segment with a 

 large red, dorso-medial spot, extending from the anterior margin about 

 two-thirds of the length of the segment, narrowly interrupted in the 

 female and slightly more interrupted in the male, with short erect 

 reddish pile; laterally from this spot, in the female, with yellow pile, 



