50 | Psyche [April 
Tachydromia sens. str. 
Minute, slender flies of shining jet-black color and almost devoid 
of hairs and bristles. Head globular, eyes large, with large facets, 
in both sexes broadly contiguous on the face; front narrow, its sides 
nearly parallel, and but slightly diverging toward the vertex; three 
ocelli present; occiput broad, produced sub-conically at the neck and 
provided with sparse short bristles. Antennae short, two-jointed, the 
outer joint short rounded oval, with the long slender nearly bare 
arista terminal or nearly so. Proboscis shorter than the head, rigid, 
vertical: palpi applied against the proboscis and tipped with several 
short bristles. 
Thorax longer than broad, not greatly convex, not truncate in front 
but considerably narrowed from the wings forward; humeri remarka- 
bly enlarged and separated from the narrow central part of the meso- 
notum by more or less deep furrows; a prealar lateral bristle on meso- 
notum; scutellum normally with two pairs of short marginal bristles, 
the basal pair microscopic, usually no other thoracic bristles or hairs 
present. Hypopygium small, more or less globular, or triangular in 
outline, terminal. Legs slender, the front femora somewhat thickened, 
devoid of bristles, but with microscopic hairs, those of the under side 
of the front tibiae serrately arranged, no spurs or conspicuous spines 
present. Sometimes the male legs have small spines on the middle 
femora or tibiae beneath. Wings narrow, costa ending at the fourth 
vein and sometimes thickened beyond the insertion of the first vein, 
hind margin of the wing short ciliate; no trace of an anal cell present. 
Our known American species of Tachydromia divide nicely into two 
groups. ‘The first of these includes slender species with elongate 
wings and legs. This group is typical of Tachydromia and is largely 
represented in the palaearctic fauna. The second group is more 
aberrant. Our species will probably be separated ultimately from 
Tachydromia as several genera, but for the present it would be quite 
unwise to do so. It is unfortunate that the small size and difficulty 
of capture of these species are responsible for their scarcity in collections. 
Undoubtedly we know but a fraction of the forms the world over, and 
until our collections are more complete we cannot hope to understand 
the relationships of these interesting little flies. 
The typical Tachydromias are shining black, nearly bristleless flies 
and have a dark band, or two dark bands, across the wings. ‘The 
