38 
DR ALFRED E. CAMERON. 
environment. But these responses must be described and the conditions influencing 
them as well, so that a descriptive aspect is an essential part in all phases of ecology. 
In the study of the responses of an individual, an order, or an association, pure 
description of the responses is necessary ; but a description which will at once 
describe and show the working of the processes by which the results were produced 
is of quite a different order. This phase of explanation has been most concisely 
expressed and applied by the students of the physical sciences, and biologists may 
profit much from a study of their methods.” Therefore, for the sake of accurate 
deduction, a method of measuring all the important factors of an environment which 
are likely to influence its biota is absolutely essential, and the reason why plant 
ecology is now quite a well-ordered and organised science is due to this very fact. 
It was almost essential that plant ecology should have precedence oyer animal 
ecology in point of time, because the latter involves a knowledge of the former, and, 
indeed, it will likely prove true, as Vestal* has remarked (p. 13), that plant and 
animal associations are co-extensive and to a large extent interdependent, the animals 
being entirely dependent upon the plants, speaking broadly, and the plants being 
partly dependent upon the animals. This view-point has not been neglected in the 
present study, but the author recognises the difficulty of superimposing the structure 
of the insect association so as to show how it coincides exactly with that of the 
plant association. The problem might be tackled equally well from one of two 
standpoints : — 
1. The insect proposition wherein, with a species, genus, family or order as the 
unit, an attempt is made to weave the web of which the physical and vegetational 
factors are the warp, the insect unit, its activities and behaviour, the woof. 
2. The environmental aspect in which the unit is represented by the environ- 
mental factors of the habitat, and the relationships of all insects of various orders, 
family, genus, and species to these factors and to each other are discussed. 
The first of these methods is perhaps the one most likely to be productive of 
detailed and accurate results. By multiplying the unit to include, say, every family 
represented in the habitat, our knowledge of any one is likely to be very exact. 
Necessarily, this method entails much application, besides time and labour. The 
second is more general, but has the advantage that by including all insect species in 
one study, it treats of the sum-total of biographical relationships and the interacting 
influences of every physical or other factor and the individual insect units. The 
latter of these is the method which has been adopted for this paper. But, either 
way, although the manner of attacking the subject may differ, the ultimate result 
would be the same. 
* Vestal, A. C., “An Associational Study of Illinois Sand Prairie” Bull. III. State Lab. Nat. Hist., 1913, 
vol. x, art. 1. 
