THE FOOD RELATIONS OF THE CARABIDJE AND 
COCCINELLIDA5. 
By S. A. FORBES. 
A group or association of animals or plants is like a single 
organism in the fact that it brings to bear upon the outer world 
only the surplus of forces remaining after all conflicts interior to 
itself have been adjusted. Whatever expenditure of energy is 
necessary to maintain the existing internal balance amounts to so 
much power locked up, and rendered unavailable for external use. 
In many groups this latent energy is so considerable and is liable 
to such fluctuations, that a knowledge of its amount and kinds, 
and of the laws governing its distribution, is extremely important 
to one interested in measuring or foreseeing the sum and charac- 
ter of the outward-tending activities of the class. 
This seems especially true of the insect world. If the checks 
upon the multiplication of insects and upon their average length 
of life which are due to insects themselves were to be suddenly 
removed, there is much reason to suppose that the total external 
effect of the class would be very greatly intensified, at least for a 
time. 
Whether our purpose be merely to understand the internal 
economy of insect life as a part of the general system of nature, 
or to apply such knowledge to a regulation of the depredations 
of insects upon plants and animals, it is equally necessary that we 
should know the character and extent of the conflicts which pre- 
vail within the class, and should understand how the various sub- 
ordinate groups limit each other’s numbers and activity, either 
indirectly by competition, or directly by destruction. 
The following notes are a contribution to a more exact knowl- 
edge of this subject than has hitherto prevailed. The view of 
the functions of the two principal predaceous families of Coleop- 
tera (Carabidae and Coccinellidse) which is common among 
