1924] North American Species of Opacifrons and Pteremis 127 
tip, vein four faintly produced to wing-margin; vein five prod- 
uced one-third distance from outer crossvein to v/ing-margin; 
discal cell broad. Abdomen cylindrical, very short, but little 
more than half as long as thorax; second segment as long as 
third. Halteres yellow. Length: 3 mm. 
Type. — Male: Pullman, Wash. June 10, 1911. (Melander.) 
Paraiype . — A single specimen from Pateros, Wash. (Melan- 
der). 
Leptocera (Opacifrons) pellucida n. sp. (Fig. 8.) 
Opaque black. Front convex, two-thirds as broad as deep, 
slightly gray dusted except on the divergent stripes and lower 
orbital stripes; lower fronto-orbital bristle three-fourths as long 
as upper; orbital setulae microscopic; interfrontal bristles in 
four pairs, the anterior and posterior pairs weak, the middle two 
pairs long and cruciate; interfrontal setulae microscopic; face 
and cheeks yellow; face deeply concave in profile; anterior 
margin of epistome slightly projecting; clypeus not visible from 
in front; cheek at vibrissal angle one-fourth as high as eye; oral 
setulae weak, hair-like; buccal setulae in three pairs, the anterior 
pair stronger than the others, bristle-like; antennae fuscous, 
third joint oval, equal in length to second; arista two and one- 
half times antennal length, pubescence microscopic. Mesonotum 
with three pairs of dorsocentral bristles, increasing in size post- 
eriorly; discal setulae in six rows between anterior pair and two 
rows between posterior pairs of dorsocentral bristles; scutellum 
triangular; marginal bristles four; pleurae with gray pollen; pleu- 
ral sutures reddish; sternopleurae with a strong posterior bristle 
and two small anterior setae. Legs brown; front femora with 
hair-like bristles; middle trochanter with a weak bristle; middle 
femora with five antero-preapical bristles, increasing in size 
apically, middle tibia with two pairs of extensor bristles, one 
on basal-fourth and one on apical fourth; hind metatarsi two- 
thirds as long as next joint. Wings hyaline; veins brown; 
costa extended slightly beyond third vein, second and third 
sections subequal; discal cell short; outer cross vein nearly as 
