1925] New Species of North American Dolichopodidce 185 
while in the older species they are only narrowly black on upper 
edge; all femora and tibiae are wholly black in appendiculatus , 
while in this form the middle and hind femora are almost wholly 
yellow, the fore and middle tibiae are more or less yellow at base, 
at least above, the joints of the tarsi are of somewhat different 
lengths in the two species, the measurements of the new form 
are given above; the joints of the middle tarsi of appendiculatus 
are as 47-27-27-15-15; and those of posterior ones are as 40-48- 
29-17-13; the wings in the two forms are about alike. 
Hercostomus purpuratus sp. nov. 
Male: Length 3.5-4 mm. Face covered with white pollen, 
wide, concave almost to the lower edge, there not being any 
very distinct separation between the upper and lower parts; 
oral margin straight, a little projecting. Front shining blu 
with purple reflections. Antennae black; first joint as long a 
second and third taken together, the latter two taken together 
nearly round in outline, the arista being inserted near the middle 
of their upper edge, its pubescence long. Palpi black with black 
hair. Orbital cilia wholly black. 
Dorsum of thorax and the scutellum purple or violet, the 
edges more blue, the front slope and the pleurae greenish; pollen 
on the dorsum brown, on the pleurae white. Abdomen dark 
green with black hair. Hypopyigum black, its lamellae large, 
nearly round in outline, sordid white with broad black border, 
which is jagged and bristly; inner appendages whitish, lamel- 
la-like, widened from the narrow base to apical margin, they have 
several minute hairs near the apex. 
All coxae black; anterior pair with small black hairs on the 
front surface and a row of bristles at tip. All femora and tibiae 
yellow, upper edge of anterior femora brown, sometimes they 
are almost wholly yellow; posterior tibiae a very little brownish 
at tip on inner side; fore and middle tibiae with strong bristles. 
Posterior femora on apical half and their tibiae on basal half with 
long, delicate, brown hairs on lower posterior surface; these 
hairs are as long as the width of the femora; posterior tibiae 
with a row of four large bristles on upper posterior edge of basal 
