14 
for discussion, we observe at once that the figures for wheat in¬ 
crease regularly from 1,311 acres per township, where the injury 
was none, to 3,189 acres, where the loss was nearly complete. An 
inspection of the columns for the other crops shows us that here 
the grass areas remain about the same, neither rising nor falling, 
if we take the list together; but that the figures for corn and oats 
clearly show a tendency the reverse of that observed in Southern 
Illinois; for while the successive numbers run somewhat irregu¬ 
larly, the whole series is clearly a descending one. Certainly, 
therefore, we must conclude that in this great territory increased 
injury to corn goes along with an increased acreage in wheat, as 
in Southern Illinois; but as this is also attended by a decreased 
acreage of corn and oats, it remains for us to determine whether 
the greater damage to corn may not all be connected with this 
latter fact,—may not be due simply to a more concentrated attack 
in the smaller corn area. A simple calculation demonstrates, how¬ 
ever, that the average increase in the series of figures for wheat, 
(24 per cent.) is nearly five times as great as the average inverse 
ratio in the figures for corn (5 per cent.) and six times as great 
as for oats (4 per cent.). In other words, as the wheat area in¬ 
creases many times faster than the corn area decreases, the in¬ 
creased wheat area must be held to have much more to do with 
the greater chinch-bug injury than does the decreased corn area. 
From this table we seem to learn that in the beginning of a 
chinch-bug outbreak the area in wheat has much more to do with 
the continuance and increase of injury than that in any other 
crop; that the acreage of oats, corn, and grass has then, in fact, 
no apparent influence, where wheat is also raised. 
The separate tables for the three subdivisions of Central Illinois 
simply show in each the same state of facts apparent in the more 
general exhibit, and are consequently not here reproduced. 
i 
Table III. 
Northern Illinois , 224 Towns. Injury to Corn , 1887, compared 
with Crop Areas for the Same Year. 
Degree of Injury. 
No. of 
Tps. 
Wheat. 
Barley. 
Rye. 
Oats. 
Corn. 
Grass. 
None. 
147 
343 
152 
375 
3,119 
4, 628 
8,173 
Little. 
48 
338 
165 
427 
3,199 
4,734 
7,976 
Moderate. 
10 
324 
136 
340 
2,952 
3,786 
7, 360 
Considerable. 
16 
335 
165 
251 
3,169 
4,569 
6,957 
Great. 
2 
431 
9 
368 
3,115 
5,065 
9,632 
Very great. 
1 
213 
10 
14 
445 
1,020 
2,526 
As is sufficiently evident from Table III., reports from Northern 
Illinois can scarcely be used in this branch of our discussion, 
both chinch-bug injury to corn, and the area in wheat being of 
so little importance that whatever slight effect one may have had 
upon the other, is completely lost to view in the presence of other 
causes of variation. Only the four minor grades of the scale of 
