6lO CALIFORNIA ACADEMY OF SCIENCES. 



rowly and faintl}' fuscous marginate, the halteres are 

 black except the palHd stalk, and the wings have no stig- 

 mal spot, but the two costal veins are brown distally. 

 The small humeral callosities are yellowish, and the scu- 

 tellum and prescutellar callosities are brownish 3^ellow. 

 I mention these points because Osten Sacken states in 

 the Biol. Centr.-Am., Dipt, (i, p. 165), that O. hiimcralis 

 O. S. and O. incidtiis O. S. are the only North American 

 species of the genus with the humeral callosities of a paler 

 color than the thorax. Outside the small yellow anterior 

 callosities, and adjoining them, there are much larger 

 dark brown humeral callosities. 



SYRPHID^. 

 32. MiCRODON VIRIDIS n. Sp. 



San Jose del Cabo, Baja Cahfornia (Eisen). One fe- 

 male. 



Length, 7 mm. Bright green. Face and front brill- 

 iant bright green, the latter with a slight bluish reflection. 

 Face with dense whitish pile, front with less dense black- 

 ish pile. Antennae brown, first two joints somewhat shin- 

 ing, third joint with an opaque whitish bloom in certain 

 lights ; third joint hardly shorter than first. Thorax green 

 with a purplish luster in disk, scutellum bright green with 

 two moderately approximated rather slender sharp spines. 

 Thorax and scutellum with whitish pile. Pleurae bright 

 green, whitish pilose. Abdomen bright green, somewhat 

 purplish on hind half and sides; the whole with whitish 

 pubescence shorter than that on thorax and scutellum, 

 but that on sides and extremity is longer than the dorsal 

 pubescence. Venter greenish, less so on sides. Femora 

 bright green, the tips and whole of tibiae yellowish with a 

 brownish tinge, hind tibiic with a median green spot on 

 outer surface. Tarsi dark brownish, hind metatarsi de- 



