1915] Ecological Foundations of Applied Entomology 5 
Certainly, also, it is dynamic action and reaction between 
organisms and their environment which give ecology its main 
interest and importance. Status, genesis, and succession, 
organisms share with stones and soils and geological strata; 
but there is no ecology of such inanimate objects because they 
lack the intensity, variety, complexity, and quickness, of 
response to dynamic impression which organic ecology connotes. 
Water-spouts, clouds, flowing streams, winds, windmills, flames 
of fire and gasoline engines, are seats and centers of rapid action 
and reaction, but simple and uniform as compared with that 
of the living animal or plant. We may discuss their dynamic, 
static, and successional relations to their environment, if we 
choose, but we are agreed not to call these ecological. This is 
a term which we confine to living organisms; and it is indeed the 
special character of their reactions which enables us to dis- 
tinguish organisms as alive. 
Furthermore, there can be no doubt that it is primarily 
the dynamic factor only in ecology which interests the eco- 
nomic entomologist. It is only what insects do which gives 
them any importance to the economist, and it is only what can 
be done to them or about them in turn which gives applicable 
value to our knowledge of them and of their economy. We 
wish to know where they are or may be, how they are asso- 
ciated, and from whence they have come and by what they are 
likely to be succeeded, simply because their activities make 
them important to us. If they were inert we should not care. 
I must further distinguish briefly between the ecology of a 
species or larger taxonomic group on the one hand and that of 
a local miscellaneous assemblage of organisms on the other. 
We may have an ecology of Aphis maidiradicis, for example, 
or of the family Aphidide in general wherever they occur; and 
we may also have an ecology of all the inhabitants of the corn- 
field considered as a group of plants and animals associated 
in a natural habitat. From this point of view, we see applied 
entomology especially interested, sometimes in associational 
or habitat ecology, such as that of the household insects or 
the insects of the forest or the truck-farm or the orchard, and 
sometimes in species ecology or taxonomic ecology—that of 
a single economic insect species, for example, or that of the 
insect associates of a single crop plant, or the several mosquito 
species serving as carriers for a single disease-producing parasite. 
