30 JOURNAL OP ECONOMIC ENTOMOLOGY [Vol. 2 



teristic associations of plants and animals — those of the pasture, the 

 oats field, and the like — and its relations also to associations preceding 

 it on its own area. As a biological association the inhabitants of the 

 corn field are variously related to each other — as competitors, as 

 enemies, as parasites, as cooperating partners, or as mere indifferent 

 companions, and their varying actions and interactions make up the 

 general ecological system of this corn field situation. The leading 

 members of this association, the kinds of organisms which may almost 

 invariably be found together in it, are certain grasses — species of 

 Setaria and Panicum especially; and certain smartweeds or heart- 

 weeds — species of Polygonum — all of which start spontaneously from 

 the seed in very early spring; the corn plant itself — whose dominance 

 gives its name to the association, the corn-field ant {Lasius niger 

 americanus) , the corn root-aphis, the corn root-worm, the white-grubs, 

 and the ear- worm ; and to these we must add two other members of the 

 group, without which there could have been no cornfield in the be- 

 ginning, and none could continue so much as a single year- — that is, the 

 horse and the man. The man, the horse, the corn plant, the smart- 

 weed, the two grasses mentioned, the ants, the aphids. the grubs, and 

 the ear-worm are the essential members of this association ; but with 

 these, I need not say, we must often include many other occasional or 

 Jess conspicuous members — the wireworms and the bill-bugs, if a pas- 

 ture or meadow has preceded corn within a year or two ; the cutworms 

 and the army-worm, perhaps, in spring, and the grasshoppers in fall, 

 if such an association is established beside it ; many species of birds, 

 most of which are. as a rule, scarcely more than accidental visitants; 

 the moles, the ground-squirrels, and the mice, which have their more 

 or less definite reasons for frequenting it or for residing in it. 



If we analyze the relations of these various inhabitants of the field 

 we find that three of these kinds form a cooperating partnership and 

 that two of them form another — the man. the horse and the corn plant 

 in one such group and the corn root-aphis and the cornfield ant in 

 the other. The interests of the former group are in open opposition 

 to those of all the other inhabitants of the field, so much so that this 

 group would profit greatly by the extermination of all the rest; and 

 its dominant agent, man, being more or less aware of this fact, he seeks, 

 as a rule, to destroy them all as completely as he can. He fails to 

 do so completely, notwithstanding his best endeavors, because some of 

 his competing associates are really better adapted to the situation than 

 the corn, the horse, and the man themselves ; and, furthermore, because 

 several of the competitors of this dominant group thrive most by the 

 very measures which it takes in its own immediate interest. The ear- 



