176 Notes on Insectivorous Coleoptera. 
ly limited by the numbers of their food species. We 
should remember, in this connection, that we cannot or- 
dinarily expect of any predaceous animal that it will do 
more than to eliminate the excess of the species it preys 
upon, keeping their numbers down within certain con- 
stant limits. As a prudent sovereign finds it worth while 
to maintain a much larger fighting force than is neces- 
sary to the ordinary administration of his government, in 
order that he may have always a reserve of power with 
which to meet aspiring rebellion, so it is to the general 
advantage that carnivorous insects should abound in 
larger numbers than could find sustenance in the ordi- 
nary surplus of insect reproduction. They will then be 
prepared to concentrate an overwhelming attack upon 
any group of insects which becomes suddenly superabun- 
dant. It is evidently impossible, however, that this 
reserve of predaceous species should be maintained un- 
less they could be supported, at least in part, upon food 
derived from other sources than the bodies of living 
animals. 
