SYNOPSIS OF NORTH AMERICAN SYRPHID.E. 13 



on, aud resembles that of Couops, while the bod^^ is that of an exotic 

 Micn)don.' We may with safety, therefore, strike out the geuiis and 

 species from among the number of existing- forms." Osten Sackeu, 

 Bull. Bull' Soc. ^^at. Sci., Nov., 1875. 



" Since writing the above I have seen the specimen and can only con- 

 firm the statement. The body seems to belong to Microdon aurifex 

 Wiedemann." Osten-Sacken, Cat. Dipt., 243.] 



CHRYSOTOXUM. 



Chrysotoxum Meigeu, iu Illiger's Magazine, ii, 259, 1803. 



Rather large, thiidy pilose, or nearly bare species, black, with bright 

 yellow markings on head, thorax, aud abdomen. Head as broad or 

 scarcely broader than the thorax. Antennae elongate, longer than the 

 head, porrect, situated upon an obtuse prominence; first two joints of 

 nearly equal length, the third elongated, spindle-shaped, before the mid- 

 dle with a thin, small, bare arista. Face broad, descending somewhat 

 below the eyes, below the antennae gently excavated in profile, and with 

 an obtuse tubercle on lower third. Eyes pilose (in some exotic species 

 bare), contiguous iu the male. Abdomen more than twice as long as 

 the thorax, beyond the middle broader than the thorax, elliptical, 

 strongly arched, with thin lateral borders; hypopygium usually con- 

 cealed. Legs comparatively weak, hind femora elongate, hind metatarsi 

 as long as the remaining joints together. Third longitudinal vein of 

 the wings with a distinct curvature into the first posterior cell ; first 

 posterior cell closed near the border of the wing ; small cross-vein a lit- 

 tle before the middle of the discal cell, a little oblique. 



In addition to these structural characters, the species show a remarka- 

 ble resemblance of coloration, which I give here to save repetition. 



Face and cheeks yellow, the former with a black stripe running from 

 the base of the antennae to the oral margin, the cheeks also with a 

 black stripe from the eye to the mouth. Antennae black; frontal trian- 

 gle with a black spot above the base of the antennae; front iu female 

 black, with a cross-band near the middle of whitish pollen. Thorax 

 black, but little shining; on each side, with a yellow interrupted stripe; 

 in the middle with a pair of slender, whitish pollinose stripes, obsolete 

 behind. Scutellum yellow, across the disk more or less translucent dark 

 colored. Pleurae with one or more yellow spots. Abdomen black, but 

 little shining ; second segment with an arcuated, interrupted cross-band ; 

 each of the following with an arched, anterior cross-band, and the pos- 

 terior border, yellow. Legs yellow, sometimes the femora more or less 

 blackish at the base. Wings nearly hyaline, with an anterior brownish 

 border. 



This genus has always been more or less of a problem to dipterolo- 

 gists. The characters that seem to distinguish the species are hard to 



