The Food Relations of the Garabidce and Coccinellidce. 
86 
which could thus be acquired by patient study, was often quite 
surprising. While it was of course rarely possible to distinguish 
species, or even genera, all the fragments could usually be classi- 
fied with some fair degree of definiteness; and there was com- 
monly no difficulty in making satisfactory estimates of the ratios 
of the different food elements present. 
In some of the most important cases, the facts elicited were of 
the highest degree of exactness. Several collections of preda- 
ceous beetles were made in situations where some particular 
species of noxious insect was especially abundant, with a view to 
determining to what extent the latter was preyed upon by its 
supposed enemies. In such cases it was not difficult to tell with 
certainty, even from very minute fragments, whether the given 
insect had been eaten or not. Even where no solid structures 
were present, and the contents of the alimentary canal were 
entirely fluid, it was still usually possible to say whether these 
fluids had an animal or a vegetable origin. After many observa- 
tions and some experiments, it was found that partially digested 
animal food in the stomach of a beetle was commonly bathed in a 
black juice, which, when examined under a high power of the micro- 
scope, was seen to contain nothing but a minutely divided flocculent 
matter, probably composed of irregular aggregations of 
fat droplets and other organic particles. This fluid was never 
found in connection with purely vegetable contents, but some- 
times filled the stomach alone, and contained nothing to indicate 
its origin. In all the latter class of cases I have regarded it as 
proof that the food had been derived from animal sources, proba- 
bly usually consisting of the juices of insects recently captured. 
For the determinations of the fungi mentioned herein, I am 
indebted chiefly to Prof. T. J. Burrill, of the Industrial University 
at Champaign. 
The insects dissected for this paper were partly obtained in the 
course of miscellaneous collecting, and partly secured for me 
especially for the purpose, by one of my entomological assistants, 
Mr. F. M. Webster, who kept careful notes of the situations in 
which the specimens were taken, the hour of the day when they 
were captured, and the objects upon which it seemed probable 
that they had lately fed. Examples of the latter were also fre- 
quently bottled with the specimens, for comparison. The special 
