384 The American Naturalist. [May,. 
In all I have secured some fifteen specimens of this little 
acarinid, which is the smallest form yet discovered in the 
cavern. It occurs on the underside of damp stones and sticks, 
in association with the thysanurids, which are described herein, 
and is easily distinguished i in collecting. The very long first 
pair of legs give it a most peculiar aspect, and as they are al- 
ways in somewhat rapid motion they serve to discover the 
little insect to the observer. Then, too, the species has the 
curious habit of raising itself up so that it stands on the first 
and fourth pair of legs when disturbed. It is exceedingly slow 
in its movements. Vision is impossible in the cave, notwith- 
standing its bright eyes, and possibly the bristles or hairs of the 
posterior abdomen, on dorsal surface, have a certain tentacular 
function—using the word in the sense of organ of touch. It 
may be said that the species was originally detected, and subse- 
quently always found, by lying prone on the ground and with 
the lamp as close as possible to both face and soil. The heat . 
appears to disturb the minute specks of pale yellowish color, 
and they appear to move; then dirt and all were collected and 
transferred to the alcohol vial, and the microscope eventually 
discovered the animal. At the first and several following trials 
it was a matter of serious question whether I had really seen 
anything move, so small are the objects. Like many another 
form the original discovery of this one was an accident. 
DIPTERA. 
‘Limosina stygia Coquillett. Nov. sp. 
“ Male and female specimens. Black, subshining, the palpi,- 
front coxæ, apices of femora and bases of the tibiæ (most ex- 
tended on the front pair), also bases of the tarsi and of the 
halteres, yellowish. Middle tibiæ each bearing a bristle on the 
outer side above the middle, a pair at the apex on the outer 
side and a single one on the inner side at the tip; hind tibiæ 
destitute of a spur at the tips; first joint of hind tarsi one and 
one-half times as thick as, but only two-thirds as long as, the 
second, twice as long as broad; second joint one and one-half 
times as broad as, and one wid one-third times as long as, the 
third; remaining joints slightly broader than but only two- 
