378 The American Naturalist. [May, 
as being new. For the Diptera, Mr. D. W. Coquillett, of the 
Department of Agriculture, Washington; for the Acarinz, 
Thysanure, Therididæ and related forms, Mr. Nathan Banks, of 
Sea Cliff, New York; for the microscopic plants, Dr. Roland 
Thaxter, of Harvard University. It is quite sure, therefore, 
that the determinations in these groups are quite accurate and 
authentic. For the single mollusk and the larger fungi the 
writer is alone responsible. 
The conditions under which collections are made in Mam- 
moth Cave are not of the simplest character. The cavern itself 
is very great, and the forms of life neither large, as a rule, nor 
abundant. Hours may be spent by a novitiate without any 
success attending his efforts, and it is only after much search 
and repeated failures that he begins to realize that the distri- 
bution of life within the cave obeys certain laws. Animals are 
not found everywhere; nor are they found in association, except 
in a few instances. Visitors frequently spend hours in the 
cavern and fail to see any evidence of life; but one who is 
somewhat familiar with the habits of insects soon discovers 
that the same principles which govern their distribution in the 
realms of light prevail in the subterranean world. In a short 
time one soon learns where not to look for life, a fact of as great 
importance to one whose time is limited as to know where to 
look. The darkness is inconceivably great, and hangs like a 
great burden on one who seeks the smaller forms. The crude 
methods of illumination avail to lighten but a small area at a 
time, and most of the forms appear to be sensitive to light while 
not possessing organs of vision ; such, at least, is my conclusion 
after some years of collecting, though, it is true that the heat 
of the lamps may be the prime cause of the haste which many 
species evince when disturbed. From my experience in Mam- 
moth Cave I have learned that it is practically useless to hunt 
for insects where the cave is very dry ; regions of wet soil or 
sides are the most favorable localities for all the insecta. The 
smaller rills and springs in the cave usually contain an abund- 
ance of small crustaceans, but mainly of two forms; aside from 
these but one form of life is common in the water, or fairly so, 
