1930 ] 
The Food of Insects 
5 
monly restrict their hunting to the capture of a series of 
related forms or even to a single species. One American 
Aphilanthops stores only queen ants and a related European 
wasp captures ants also. Our common American mud- 
dauber wasps collect small spiders of various kinds and 
certain crabronids capture flies of a single or of several 
species. The fixity and persistence of their instincts is 
shown by the tendency of genera or larger groups to re- 
strict themselves to related types of prey, and this may 
extend to the members of a large family like the Psam- 
mocharidse, where the spider-storing habit is so general that 
the vernacular name of “spider wasps” has been bestowed 
upon them by common consent. In another group, stages 
through which the change from a somewhat indiscriminate 
diet to a specific one has taken place are still preserved. 
Thus, in the genus Sphex (Chlorion) some species store a 
variety of Orthoptera in their nests, others only a few, and 
finally some only one. As we shall see in a moment this 
condition prevailing among the solitary wasps is wholly 
analagous to that which obtains among phytophagous 
insects. 
The tendency among these diverse types of predatory in- 
sects is clearly toward a restriction of the dietary although 
we cannot consistently detect any orderly arrangement 
whereby a relationship of predators implies to any great 
extent a similarity of prey. Sufficient evidence has been 
presented, however, to show that we cannot make any broad 
generalizations. Thus predaceous insects do not exhibit the 
close correlations characteristic of parasites nor of vege- 
tarian insects. At this point, we must emphasize the fact 
that many predatory insects have narrowed down their food 
relations to a point where their direct contacts with the 
environment are restricted to certain definite components 
of the fauna of which they themselves form an integral 
part. The significance of these facts may be best understood 
after we have examined the food relations of vegetarian 
insects. 
Insects that feed on plants are far and away the most 
important series to illustrate the adherence of species or 
larger groups to restrict diet. On account of their complex 
relationships toward these plants directly, and indirectly 
