1G 
ON CONTAGIOUS DISEASE IN THE CHINCH-BUG 
(Blissus leucopterus, Say)*. 
ON THE RELATIONS OF ECONOMIC ENTOMOLOGY. 
Economic entomology is most commonly thought of as a divi¬ 
sion of entomology; and so it is, indeed, but not in the sense in 
which that statement is most likely to be taken. 
An entomologist as such is interested primarily in the study of 
insects, and other matters come into his field only incidentally 
and as a help to an understanding of his entomology; but the 
center of interest to the “economic entomologist,” so called, is not 
the insect itself but its relation to the material well-being of man. 
There is another division of biological science, little known to the 
general public by its name as yet, and but lately distinguished as 
a separate subject, but which is now commonly called cecology. It 
is the science of the relations of living animals and plants to each 
other as living things and to their surroundings generally. It deals 
with the ways in which heat and light, moisture and drouth, 
soil and climate, and food and competitors and parasites and pre¬ 
daceous enemies, and a long list of agencies additional, act upon liv¬ 
ing things, and the ways in which these living things react in turn; it 
includes, in short, the whole system of life as exhibited in the inter¬ 
actions between the plant or animal and the environment, living and 
without life. It is a very comprehensive, complicated, and important 
subject; how comprehensive and important we see at once when we 
learn that the whole Darwinian doctrine belongs to it on the one 
hand, and that all agriculture depends upon it on the other. It 
covers, indeed, the whole field of active life and all forms of mat¬ 
ter and energy as affecting living things in any way. 
Economic entomology is, of course, a division of this science of 
cecology and may be exactly defined as entomological cecology 
applied to economic interests. The economic entomologist is thus 
essentially an oecologist, engaged directly in a study of the rela¬ 
tions of insects to the pursuits and welfare of mankind, and in¬ 
directly in a study of their relations to the general system of liv¬ 
ing nature at large. 
*For general summary of economic values and results, see p. 26. 
