8 Annals Entomological Society of America [Vol. VIII, 
farmer is still practicing his art in great measure as did his 
remote predecessors, by rule of thumb. He paid us the com- 
pliment of saying that the economic entomologists of the 
country are much farther advanced in this respect than the 
agronomists—that we know more of the corn insects than the corn 
breeder knows of the corn plant. I did not tell him, as I might 
have done, that this opinion simply signified that he knew less 
of entomologists and the state of their knowledge than he did 
of corn and the corn farmer; for this is also our case. How 
many of our measures of protection and defense against insect 
depredations depend upon any precise knowledge of general 
fact or scientific principle, or are traceable to anything better 
than a purely empirical warrant? If we attempt to analyze 
what we know and what we still need to know concerning any 
one of the great insect pests before we shall be in a position 
to do all that can be done and ought to be done to restrain its 
ravages and injuries either by measures of avoidance, pre- 
vention, mitigation, or arrest, we may perhaps get a clearer, 
concrete idea of what is involved in economic entomology, 
and what are the foundations of fact and principle upon which 
it rests. 
The chinch-bug of our western grain fields has been a subject 
of close, though inexpert, observation for nearly a century, 
and of much expert study and experiment for more than a 
generation; but during this present year, in my own state, 
where we have used against it every method and device which 
we could induce those most immediately concerned to apply, 
millions of dollars worth of farm crops have been destroyed by 
it, and a large part of the rural population of whole counties 
has been brought close to economic distress and in some cases 
to financial ruin. 
We know the facts concerning the geographical distribution of 
this insect species, without which, of course, we should not 
know where to expect its ravages and to provide against them, 
but this is for us a matter of observation merely, and not of 
scientific inference or rational interpretation; we do not defi- 
nitely know what are the limiting conditions of its distribution 
in any direction. Over parts of its occupied area it is present 
only in numbers economically insignificant, and we have little 
actual knowledge why it is destructive in a part of its territory 
