54 
tance from woodlands, by driving the adult chinch bugs from the 
open fields and compelling them to resort to the grassy woods for 
food for themselves and their young. 
Severe drouth in a small-grain district has so thoroughly and 
so early destroyed the corn crop there, as to test practically the 
effect of abandoning that crop as a defence against the chinch bug. 
In the case observed, it was found that the injury the following 
season was very much less than before. As the drouth took effect, 
however, on the field grasses generally, and thus still further re¬ 
duced the supply of insect food, the result was not to be attrib¬ 
uted wholly to a lack of corn. 
A similar destruction of the corn by drouth in midsummer fol¬ 
lowed by a general winter-killing of wheat, has shown that a suc¬ 
cessive abandonment of these crops may greatly reduce the num¬ 
bers of the chinch bug, even where other conditions are very- 
favorable to it, this reduction amounting, in one such case, to one- 
half or three fourths of the number abroad the year preceding. 
Where wheat is abundant in a district very badly infested by 
chinch bugs, it is now certain that this insect may live and breed 
very successfully in early spring in oats, in young timothy and 
blue grass meadows, and even in corn. 
A thorough-going investigation of the relations of chinch-bug 
injury to the acreage of the principal farm crops of Illinois in 
1886 and 1887 shows that, where the outbreak was but just begin¬ 
ning, the wheat area had evidently much to do with the number 
and the rate of increase of the insects, a rising gradation of 
injury appearing in correspondence to an enlarging area in wheat, 
the acreage of the other crops at the same time remaining 
ea y constant or slightly declining. As the severity of the 
attack increases, however, the oats area begins to rise with the 
wheat, and may presently surpass the latter as a stimulus to the multi¬ 
plication of the chinch bug, corn and grass finally showing a like 
tendency where it has become excessively abundant and destruct¬ 
ive. Here, when the eggs of the winter brood are being laid freely 
on all the food plants of the species, the wheat area may even 
decline as one passes from districts where destruction is very great 
to those in which it is complete. This may be due to one or 
more of the following circumstances: (1.) The wheat area may be 
purposely diminished by the farmers, one year after another, as 
was certainly sometimes the case in southern Illinois in 1887, 
where chinch-bug injury had greatly lessened the yield and value 
of the crop for the season or two preceding; (2.) A change of 
feeding habits may arise among the insects themselves;* or (3.) 
there may be a spontaneous gradual shifting of the center of at¬ 
tack, due to a natural diminution in the number of insects one 
•Such variations in choice of food under different conditions are not by any means rare among 
insects. The Hessian fly, for example, is very destructive to rye in Europe, while here it is almost 
never seen in that grain; and the chinch bug itself has made in New York a severe attack on 
meadows while not noticeably harming any cereal ci’op. 
