18 



saying that the" greater was the damage, the larger was the 

 area in crops of any and all kinds capable of furnishing food to 

 chinch bugs*. 



This conclusion clearly compels at once a reconsideration of the 

 effect of wheat alone, — a re-examination of the table so made as to 

 ascertain whether the wheat area increases faster with increased 

 injury than does the area in the other crops reported. On this 

 point the indications of the table are not quite clear, but are 

 nevertheless interesting and suggestive. The increase in wheat 

 corresponding to the five available numbers of the table we find 

 to amount to an average of 31 per cent, for each step of the 

 gradation; while that of corn amounts to only 8 per cent.; that of 

 grass to 10 per cent.; and that of oats to 33 per cent.; in other 

 words, while wheat and oats have increased in about the same 

 ratio with increase of injury by chinch bugs, and bear, so far as 

 this table is concerned, the same relation to such increase, the 

 corresponding increase of corn has amounted to only about one 

 fourth that of the wheat, and the grass increase to about one third. 

 From this we are certainly justified in concluding, provisionally, 

 that, even under the extreme conditions prevailing in Southern 

 Illinois last year, the acreage of wheat has more to do with the 

 increase of chinch-bug injury to corn than the area of any other 

 crop, except, perhaps, oats; but as the latter crop, and also corn 

 and grass, seem also to favor insect increase, we find little en- 

 couragement for the supposition that under such circumstances an 

 abandonment of wheat alone will serve to control injury by the 

 chinch bug, or seriously to check its increase. 



Table II. 



Central Illinois, 397 Towns. Injury to Corn, 1887, compared 

 with Crop Areas for the Same Year. 



Degree of Injury. 



No. 

 of Tpa. 



Wheat. 



Barley. 



Kye. 



Oats. 



Corn. 



None 



Little 



Moderate 



Considerable 



Great 



Very great 



Nearly complete 

 Complete 



244 

 73 

 14 



a3 



8 

 11 

 13 



1 



1,.31] 



2,080 

 2,368 

 2,582 



2, m 



2,949 

 3,189 

 6,113 



44 

 31 

 16 

 23 

 45 

 27 

 317 



2, 754 

 2,281 

 1,711 

 1,172 

 1,502 

 2, 134 

 2,254 

 4,257 



5,765 

 5, 045 

 4, 488 

 3, 275 

 3,003 

 4,514 

 4,428 

 7,251 



Passing now to Table II., for 397 towns of Central Illinois 

 where all the grades of injury to corn except the highest are rep- 

 resented by groups of townships sufficiently large to be available 



•As it here seemed possible that the larger area under cultivation was a consequence of the 

 -Teater and long-continued chinch bug injury with which I found it associated, and not in any 

 ease a cause, — due, in fact, to the clearing up of the richer bottom lands in Southern Ulinois. 

 vhere the partially exhausted prairie lands had repeatedly failed to yield a profitable crop,— I 

 ' horoughly overhauled my data with this point in mind, but without finding any ground for such 

 conclusion. The area under cultivation la the principal crops was greater in 1887 than in 1886, 

 but the increase was not more marked in regions badly infested than in those where the damage 

 wM less. 



