40 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 17 
been correlated and until all the factors are correlated no definite rules of 
application can be applied. 
While this great phase had been going on in the sideline of chemical 
development other entomologists had already begun the control study 
from another angle. This study to be sure had been going on for 
decades but a greater impetus seems to have been given to it during the 
last 15 years. This is a control based on the ecological study of insects 
in the broadest sense of the term. The three steps then in the progress 
of development may be compared to a great tree,—the trunk and roots 
being the morphological and the systematic, the larger limbs being the 
biological aspects and the smaller branches and the tips of the twigs 
being the grasping of the relationships of the insects to their environ¬ 
ment. 
Perhaps the first publications where this approach was appreciated 
were those by our own Dr. S. A. Forbes. A few of the other more 
important papers along these broader ecological lines are those of 
Hopkins, with his bioclimatic law and with his host selection principle as 
proved by Craighead; those of Headlee on temperature and humidity on 
insect metabolism; Shelford in his studies of environmental factors; 
Pierce on death rate and climatic condition; Sanderson on the influence 
of minimum temperatures in limiting distribution; Peairs on the re¬ 
lation of temperature to insect development; Craighead with his manipu¬ 
lation of shade for the control of the locust borer; Chapman in his 
granary weevil work and a host of others. McColloch and Hayes in 
their studies of '‘soil temperature and its influence on white grub ac¬ 
tivities” are likely to get some interesting leads in combating injurious 
soil insects. Newell and Smith in the so-called “Florida method” of 
boll weevil control have taken advantage of a knowledge of the ecology 
of the boll weevil in making more effective the use of insecticides. 
These and many other ecological studies offer uncommonly interesting 
material for the present day entomologist to follow. The lead seems to 
be a good one and may take us into newer and certainly wider fields. 
The paper of J. DeWitz in the Bulletin of Entomological Research 
(1912) on “The Bearing of Physiology on Economic Entomology” 
and the wonderfully interesting address of the late Dr. Hewitt to this 
Association in December 1916 on Insect Behavior show many of the 
reactions I have in mind. 
Today there are insects doing a tremendous amount of injury that we 
say cannot be controlled. Some entomologists have even given up the 
hope of ever controlling these insects. I believe that someone here today 
