28 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



thick, shining black at the base, but becoming lighter towards the tip, which 

 bears well developed yellow appendages. Pleurae above metallic bluish 

 green, below deep metallic blue, dusted with gray. Coxae and legs pitchy 

 yellow, coxffi and tarsi of a somewhat darker tint than the femora and tibiae. 

 Hairs on the anterior surfaces of the coxse and the few bristles above the 

 insertion of the fore coxse, white. First joint of hind tarsus plain, second 

 joint about one and two-thirds times as long as the first joint. Wings hyaline 

 and iridescent. Veins yellow, lighter towards their bases. Tips of the third 

 and fourth veins rather close together; distal segment of fifth vein one and 

 one-half times as long as the posterior cross-vein. Tegulae and halteres 

 light yellow, the latter with white cilia. 



Female. Length 2-2.25 mm.; length of wing 2.5 mm. The coloring is 

 the same as that of the male, except that the first abdominal segment is 

 thickly covered with gray dust like the thorax. This may perhaps be the 

 case in well preserved male specimens also. 



Three males and three females of this pretty little species 

 were sent me by Professor J. M. Aldrich. They were 

 taken at Colfax, Washington, in July. 



30. Medeterus xerophilus, sp. nov. 

 Plate II, Figs. 33-35- 



Male. Length 1.5 mm.; length of wing 1.5 mm. Proboscis and palpi 

 small, shining, black. Face dull metallic green, not glabrous. Antennae 

 black, arista subapical, as long as the face. Front black, covered with 

 opaque gray dust. Postocular cilia pale. Thorax metallic green, thickly cov- 

 ered with gray dust. Dorsal bristles black. Scutellum of the same color as 

 the thorax, with four bristles. Abdomen somewhat flattened dorsoventrally, 

 black, subglabrous, its hairs of an uncertain color, pale in some lights, dark 

 in others. Hypopygium small, slender, more glabrous than the remainder of 

 the abdomen. Appendages minute, yellowish. Pleurae black, thickly cov- 

 ered with gray dust above, more thinly towards the coxae. Above the fore 

 coxae there are a few white bristles. Coxae black with pale hairs. Legs dark 

 brown or piceous, with yellow knees and the bases of the anterior metatarsi 

 broadly yellow. Hind metatarsi plain, second joint only one and one-half 

 times as long as the metatarsus. Wings rather short and broad, brownish 

 gray, with brown veins growing yellowish towards their bases. Third and 

 fourth veins ending rather far apart, the latter in the very tip of the wing. 

 Posterior cross-vein twice as long as the distal segment of the fifth vein. 

 Sixth vein very faint. The discal cell is rather broad at its proximal end. 

 Halteres yellow. Tegulae brown, with brown cilia. 



Female. Length 2 mm. ; length of wing 2 mm. It agrees with the male 

 in coloration. The ovipositor is not exserted as it is in the females of many 

 species of Medeterus. 



