178 AMERICAN MIDLAND NATURALIST. 
less can the slow moving snails and mussels escape danger 
where the bottom on which they rest is torn up or buried 
inches deep under mud or stones, or where logs, plants or 
other objects to which snails cling are dashed against banks 
or whirled away by raging torrents. 
nds and lakes are also made turbid by the silt of 
plowed fields and the smaller Crustacea are smothered by the 
muddy water. Draining destroys marshes and annihilates 
aquatic plants and animals by the billion. - The larger lakes 
and rivers are doubtless affected less than the small ones, but 
the character of their waters also is changed and the weaker 
species must suffer in consequence. In recent years the pearl 
mussel industry has grown so rapidly that mussels have be- 
come scarce where they were once abundant and there is dan- 
one they may be exterminated unless the industry is reg- 
ulated. 
In spite of the fact that we have no recorded informa- 
tion in regard to the former abundance of Mollusca and Crus- 
tacea, and little knowledge of their present number, there can 
be no doubt that both groups have diminished. With the ex- 
ception of the river mussels, none of the species of either class 
found in the State have any direct value to man. urn- 
ish, however, the basis of food supply for the vast majority 
of fishes and are also eaten by many birds. Their diminution 
is therefore an economic loss, although some of the conditions 
that have caused them to dimish may more than counterbal- 
ance the loss. 
INSEC1S. 
Mr. Max Ellis, of Indiana University, has contributed 
the data and generalizations for this section of the 
paper, although his notes have been rewritten to form a con- 
nected account. 
Probably many insects have increased, and several have 
been added to the fauna, by introduction or migration. Un- 
fortunately we have little knowledge of the vast majority of 
Species and this account is necessarily limited to a few of the 
arger species and a few of considerable economic importance. 
During the larval stage, many insects are dependent upon one 
or few species of plants for food, and since they have not the 
ability to move rapidly or far, their presence or absence in any 
ocality may be determined by the presence or absence of a 
certain plant. 
=~ Butterflies are doubtless better known than any other in- 
. Sects and our knowledge of their range is more complete. 
Blatchley (’91) has published a list of the species known to 
occur in the State, with localities at which they had been re- 
