12 



I have selected, first, for examination the relation betw^sen 

 injury by chinch bugs to corn in 1887, and acreage in wheat 

 and other grains for the same year. As the chinch bugs bred in wheat 

 in spring resort finally to corn, and rear there almost exclusively the 

 second brood of the season, we should expect to find any increase 

 in chinch bugs due to a large wheat acreage, expressed in a larger 

 degree of damage to corn in the same territory. Examining first 

 the table for Southern Illinois and throwing out the first three 

 groups of townships because too small to give an average of any 

 value, we observe a slightly irregular but unmistakable increase 

 in average wheat acreage as the chinch-bug injury to corn in- 

 creases. Seven towns reporting the injury to corn as "consider- 

 able," have a wheat area of 1,905 acres each, while twenty-eight 

 towns where the corn was totally destroyed averaged two and a 

 fourth times as much — 4,266 acres each. The intermediate num- 

 bers form an ascending series, except that the second one is un- 

 duly high, but still below the last. This plainly shows that in 

 Southern Illinois, in 1887, the wheat area was much greater, on 

 the whole, where the damage to corn by chinch bugs was the 

 greater, and greatest of all where the destruction was complete. 



Immediately, however, an interesting and important question 

 arises. Is it not possible that in these towns less corn was raised 

 where there was more wheat, the area in the two crops varying 

 inversely, the great chinch-bug injury to corn apparent being then 

 due to the smaller corn acreage, and the consequent closer con- 

 centration of insects in what corn there was? 



The column headed "corn" in the same table gives the answer to 

 this question, and from this we learn that the corn area did not 

 decrease as the wheat area enlarged, but that, on the contrary, it 

 actually increased (though irregularly) as the wheat did.* Cer- 

 tainly, therefore, the corn was not more injured only because there 

 was less of it. , 



That the corn acreage should increase with chinch-bug in- 

 jury to the crop is a surprising fact, and suggests a glance at 

 the columns for oats and grass (barley and rye being insignificant 

 crops in Southern Illinois), and here we learn that the area in 

 these two great staples also was the greater where chinch bugs 

 were the more abundant, — the increase in the numbers for these 

 crops being an almost continuous one from 1,114 to 2,671 for oats and 

 from 2,121 to 2,975 for grass. We reach, consequently, the interesting 

 and unexpected generalization that where the destruction of corn 

 by chinch bugs in the southern part of the State was greater, 

 the area was greater in wheat, oats, corn, and grass,— that is in the 

 staple farm products of the region. This is little more than 



•The flFHt twf) iiiunberH in tliiH HcrioH of flvo amount to 5.47(1 and the last to ((.OUi. 



