1924] North American Species of Opacifrons and Pteremis 123 
6. Second section of costa longer than third; face, cheeks, and 
two spots on front slivery pollinose; notum glossy black; 
acrostichal setulse very short; hind metatarsi one-half 
as long as second joint; abdomen piceous, hind margins 
of segments narrowly yellowish; halteres whitish. Fig. 
4 .wheeleri n. sp. 
7. Lower front reddish; interfrontal bristles not cruciate, the 
lower pair weaker than the others; last section of third 
vein slightly curved up; face and cheeks black or grayish; 
second section of abdomen as long as the next two. Fig. 
7 coxata Stenh . 
Entire front black; face and cheeks yellow or with the 
posterior portion of cheeks blackish; lower two pairs of 
interfrontal bristles cruciate: second segment of abdomen 
but little longer than third. Fig. 9. . convexa n. sp. 
Limosina (Opacifrons) grandis n. sp. (Fig. 1.) 
Subshining black. Front decidedly convex, opaque, almost 
twice as broad as deep; the divergent stripes velvety black; 
setigerous stripes and frontal triangle slightly silvery pollinose; 
vertex with a distinct silvery pollinose spot on each side and one 
directly in front of ocellar triangle; fronto-orbital bristles nearly 
uniform in size; upper two orbital setul^ bristle-like, as strong 
as the upper pair of interfrontal bristles; interfrontal setae 
bristle-like, in three pairs, at right angles to the interfrontal 
rows; face gray dusted, slightly carinate; clypeus broadly 
visible from in front; cheeks silvery pollinose; at its narrowest 
point, one-third as high as eye; buccae with a long upcurved 
outer bristle and three small setae; oral margin with a row of 
long hairs; antennae with third joint rounded, much larger than 
second and with minute whitish pubescence; arista three times 
antennal length with rather long pubescence. Mesonotum with 
three pairs of dorsocentral bristles in widely divergent rows; 
acrostichal setulae strong, in eight rows between the anterior 
pair and in four rows between the posterior pair of dorsocentral 
bristles; scutellum triangular; marginal bristles bristles four; 
