1915] Ecological Foundations of Applied Entomology 17 
hand, was injuring or killing the corn, was because the per- 
meability of the coats of the embryo of the corn plant to oils 
varies with the amount of moisture in the kernel, the wet corn 
kernel absorbing these oils quickly to the injury of the plant, 
while the relatively dry kernel absorbs them slowly, with no 
injurious consequences. My discrepant results were thus due 
to mere differences of weather at planting time in the several 
cases. 
The kind of ecology which entomologists, intent on the solu- 
tion of their special problems, are not now undertaking—are 
scarcely in a position to undertake—is the formulation and 
elaboration of general principles—the laying of foundations 
broad and deep. For their emergency structures, they are dig- 
ging down a little way as well as they can, or are merely build- 
ing, perhaps, on the bare ground. But this is because the eco- 
logists have not yet built—are only beginning to try to build— 
foundation structures up to their level. When the ecological 
foundations are well and truly laid, then our entomological 
superstructures will rest upon them, as a matter of course. 
Associational ecology, a favorite subject with the pure ecolog- 
ists, is another division to which entomologists have thus far 
given little attention—too little, I think, for their own good. 
Even where we treat in a comprehensive way of all the insects 
infesting a single crop plant—deal, that is, with a mixed asso- 
ciation in which the crop plant is the prevailing, central species 
—we pay little attention, as a rule, to the ways in which the 
different insect members of the group interact with each other, 
unless, indeed, they are parasitic or predaceous. 
Pardon me if I draw once more upon my own experience for 
a simple illustration of the relations which may be made out 
by a comparison of the data of associated species. It was ina 
study, made more than thirty years ago, of the insect population 
of a strawberry plantation that I noticed the curious way in 
which three species of coleopterous larvee succeed one another in 
their injuries to the roots of the strawberry plant, the life his- 
tories of the three being so adjusted, as by a kind of dove- 
tailing process, that simultaneous competition is completely 
avoided, each species appropriating its share of the growing 
rootage of the plant in its turn, and all thus drawing from it a 
much larger food supply than if their drafts had been coinci- 
dent. This fact was the more striking when it was seen that 
