31 



gram YI. )? — ^^w first brought out on this general diagram; and 

 the more rapid decline o£ these two lines at their beginning than 

 of the line for oats — more rapid than the ascent of that for wheat. 



The whole may be generalized to the efiPect that where chinch- 

 bug injury is beginning merely, and is not yet very serious, it 

 will be greater where wheat is more abundant and where oats, corn, 

 and grass are less so — especially the latter two; but that as the 

 insect damage gradually becomes overwhelming, the wheat area 

 may be expected to diminish slowly with the heavier grades of 

 loss, the area in oats increasing rapidly at the same time, and 

 corn and grass likewise finally taking an upward turn. Otherwise 

 stated, those districts in which most wheat is raised feel the dam- 

 age first and most severely; those in which wheat and oats are 

 the principal crops next receive the brunt of the insect attack; 

 and the last to be seriously affected are those in which corn and 

 grass are the leading products. 



In brief, the lines on these two diagrams illustrate, in the first 

 part of their course, — that really representing Central Illinois, — 

 the normal relations of an at least fairly healthy agriculture; 

 while in the last part they tell the sad tale of an increasingly 

 deadly, an almost overwhelming, malady. The decline of the 

 wheat line shows the ruin of wheat culture impending, if not 

 almost accomplished in 1887; and the successive rise of the lines 

 for the other crops shows from what sources the chinch bug was 

 then drawing its principal support, and which crops it would next 

 attack most heavily.* 



The rules of practice to be drawn from the foregoing conclu- 

 sions are as follows: 1. Whatever may be done by cropping 

 against the chinch bug must be done early or not at all. If action 

 be delayed year after year until these insects become excessively 

 numerous, the abandonment of wheat or other special crops will 

 do no good, and, taken alone, may do great harm. In short, this 

 is a preventive rather than a remedial measure. 2. In the begin- 

 ning of an outbreak, the acreage in wheat, barley, and rye should 

 be promptly reduced or those crops should be wholly abandoned. 

 3. If the chinch bug continues to increase, the oats area should 

 be rapidly diminished, — corn and grass remaining the principal de- 

 pendence, and clover being substituted for the latter wherever 

 practicable. 



• It may possibly be objected to this reasoning, that since the relation demonstrated between 

 the highest grades of chinch bug in.iury and a peculiar distribution of the principal farm crops is 

 one of coincidence only, it may be that the peculiar cropping is an effect of the chinch-bug injury 

 but not in any sense a cause,— that, in other words, the farmers of the worst infested regions are 

 attempting to protect themselves against the chinch bug by lessening the wheat area, and increas- 

 ing that in oats first, and afterwards that in corn and grass. If this be so, we shall find, on com- 

 paring the areas of IHHB with those of 1887, that the oats acreage of 1887 is not only larger than 

 that for 188f), but that the ratio of increase is notably greater in those townships where chinch-bug 

 damage is very high than in those where it is but moderate; and the same may be said of corn and 

 grass. A careful comparison of the crop reports from Southern Illinois for these two years shows 

 no such relation. The area in all the crops is greater (as already remarked) in 1887 than in 188(), — 

 that is, the population iti increasing and the woodlands are being cleared up; but the ratio of in- 

 ' rease for the above crops is not greater in the worst infested counties than in those less damaged. 



