68 
vittae; three postsutural and two sternopleural macrochsetae ; scutellum 
bearing three pairs of long marginal macrochaetse; abdomen shining, 
a pair of marginal macrocha'ta' on the tirst and second segments and 
a marginal row on the third; genitalia projecting at least twice the 
length of the fourth abdominal segment beyond the latter, curved 
beneath the abdomen: tirst segment of abdomen in the female greatly 
dilated vent rally; hind tibia' not ciliate with bristles; front pul villi in 
female one-half as long as, in the male about as long as, the last tarsal 
joint; wings hyaline, a single bristle at base of the third vein, other 
veins bare, apical cell open at the extreme tip of wing, bend of fourth 
vein arcuate, hind crossvein nearly perpendicular, midway between the 
small crossvein and bend of the fourth vein; calypteres white; length, 
\ to 5 nun. Southern Illinois. Two males and one female collected by 
Charles Robertson. Type No. 3559, V . S. National Museum . .atra n. sp. 
Genus LEUCOSTOMA Meig. 
Leucostoma Meigen, in [lliger'a Magazin fur [nsektenkunde, Vol. II, p. 27!); 1803. 
Clelia Desvoidy, Bssai but lis Myodaires, p. 255; is:!". 
Psalida Rondani, Dipterologiw [talicie Prodromus, Vol. I, p. 7(!; L856. 
This synonymy is given by Schiner 1 and repeated by Brauer and 
Bergenstamni. 2 Our species are black, the palpi sometimes yellow; 
three sternopleural and usually three postsutural macrocha'ta' : 
1. Thorax shining, almost destitute of pollen, frontal vitta at the 
lowest ocellus narrower than either side of the front at the same 
point, scutellum bearing three pairs of marginal macrocha'ta', 
first two segments of abdomen each bearing a marginal pair, 
palpi yellow 2. 
Thorax opaque, densely gray pollinose, frontal vitta of female at the 
lowest ocellus twice as wide as either side of the front, palpi 
black; front of female one and one-third times as wide as either 
eye, two pairs of orbital bristles, cheeks one-sixth as wide as the 
eye-height, antenme two thirds as long as the face, the third 
joint as long as the second, arista thickened on the basal three- 
fifths, the penultimate joint shorter than broad; thorax not dis- 
tinctly vittate. scutellum densely gray pollinose, bearing two 
pairs of long marginal macrocha'ta', abdomen shining, basal 
half of the last three segments gray pollinose, tirst two segments 
destitute of macrocha'ta', those of the other two segments very 
short, genitalia of female claw-like, curved beneath the body; 
wings hyaline, third vein bearing two or three bristles near the 
base, hind crossvein straight, one and one-third times as long 
as the last section of the third vein, situated midway between 
the small crossvein and the bend; calypteres white; length, 
5 mm. Clementon, N. J. A single female specimen collected 
1 Fauna Austriaca,. Vol. I, p. 542; 1862. 
sZweif. Kais. Mus. Wien, VI, Index; 1893. 
