12 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
female; the base of the wing as far as the tip of the second basal 
cell and the bifurcation of the second and third veins is brown. 
From the point mentioned to the small cross vein, and narrowly in- 
closing the latter, there is a bright yellow area, widest at the costa 
and extending a little into the discal cell, which is otherwise brown; 
there is thus in effect a yellow band extending halfway across the 
wing, which is elsewhere brown. The effect is different from anything 
in the genus so far as have seen. The third costal segment (between 
the auxiliary and the first vein) is a little longer than the second and 
more than twice the fifth; the fourth vein is straight beyond the very 
broad bend and the apical cell is open at the costa for a distance 
longer than the anterior cross vein, or about half the posterior one. 
The second abdominal segment has no marginal bristles, but the 
third has a few small ones; the fourth has erect hairs and at the apex 
a few small bristles. The eyes in the male are almost contiguous on 
the front, being separated by only about half the width of the ante- 
rior ocellus. The middle and hind femora are dark brown for more 
than half the length and the front ones entirely, except a narrow 
space underneath at tip. 
Length of male, 13 mm.; of female, 13.5 mm. 
Described from a male and female, collected at ‘“Yungas de la Paz, 
Bolivia, 1000 M’’. Types in the British Museum. The species is 
nearest to umbrosa, but seems distinct in its vivid wing coloration, 
darker legs, etc. 
MESEMBRINELLA UMBROSA, new species. 
Mesembrinella bicolor Gieuio-tos, Van der Wulp, Biol. Centr. Amer. Dipt., vol. 2, 
1896, p. 301, pl. 7, fig. 18. 
Male.—Head, thorax, and legs rather uniformly brown in color, 
darker than in most of the species; abdomen except at base with 
some metallic blue reflections on brown ground. Front at narrowest 
only as wide as the anterior ocellus; third antennal joint brown; 
palpi and proboscis dark yellow. Thorax indistinctly darker along 
the middle on the mesonotum, hardly showing the usual stripes of 
pale pollen. Chaetotaxy: acrostichal 2 or 3, 1; dorsocentral 2, 3; 
humeral 3; posthumeral 3; presutural 2; notopleural 2; supraalar 3; 
intraalar 2; postalar 2, and asmall; scutellum with 1 apical, 2 lateral 
both close to base, 1 discal close to edge; sternopleural 2, 1; a few 
pale hairs on hind calypter, on its attaching membrane above. 
Abdomen brown, with blue reflections except at base; first and 
second segments without bristles even laterally, third and fourth 
with only a weak marginal row. Genital segments very small, brown; 
inner forceps parallel, slender, tapering, ending in a smal! up-curved 
hook; outer forceps slender and strongly bowed inward, their rounded 
tips approaching the tips of the inner pair. Fifth sternite with V- 
shaped incision, not with striking hairs or bristles. Legs uniform 
reddish yellow, the tarsi apically a little darker. 
