4 Annals Entomological Society of America [Vol. VIII, 
this signifies with respect to the ecological foundations of ap- 
plied entomology we shall be in better position to see when we 
have come to conclusions as to the meaning of ecology itself, 
and as to the general relations of that subject to entomology 
as actually applied. 
At this point I shall have to appeal to your courteous 
patience for permission to present a few elementary definitions, 
a rehearsal of which seems to me necessary to avoid possible 
ambiguity, uncertainty, or misunderstanding; especially so as 
the animal ecologists themselves are not by any means in exact 
accord as to the scope, description, subdivision, and nomenclature 
of their subject. Let us agree, then, that, for the purposes of 
this discussion at any rate, the subject matter of ecology may 
be defined as the relation of organisms to their environment, 
and that this means the whole environment, organic and in- 
organic, and any and all organisms, man included—man, in- 
deed, as by far the most important living factor, from whatever 
point of view. And let us also understand that the relations 
meant are, first, relations of interaction—dynamic relations, 
of efficient cause, and effect produced upon the organism by 
its environment and upon the environment by the organism; 
second, space relations, of distribution, position, juxtaposition, 
and association—static relations, we may call these, since they 
show the status of an individual or a group at a given time with 
reference to the various objects of its environment; and third, 
successional relations, time relations, sometimes called genetic 
because, in showing the static relations of a group in successive 
periods, they trace the genesis of the present status. 
It is evident at once that dynamic interaction with the 
environment is a cause of which static relation and successional 
relation are the effects. An organism comes to be established 
where it is, and associated as it is, by reason of the nature of 
the interactions between itself and its environment. If we 
imagine all exchange of action between the organism or the 
group and its environment to be suddenly stopped, we must see 
that the group would collapse, that the organism would prompt- 
ly perish. If the system of interactions changes, the status 
changes to correspond, and not otherwise; and if these dy- 
namic changes, however slow, are continuous over a long 
period and in the same direction, the changes of status result- 
ing have the character of a succession. 
