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counties (see Map G) lie in a compact, roughly triangular body, with 

 the Mississippi River from Randolph to Pike counties as the base of 

 the triangle and Shelby county at its apex. The uninfested counties 

 lie in an irregular zone around the margins of the infested area ex- 

 cepting, of course, on the western side. A comparison of the total 

 yield and value of all crops subject to chinch-bug attack in these two 

 ureas in 1914 ought to show how large a deficiency should be charged 

 to the chinch-bug in that year. 



It was first necessary, however, to see whether the two sets of 

 counties were sufficiently alike in average productivity to make the 

 comparison a fair one. It seemed quite possible that, altho taken at 

 random, they might be enough unlike in their agricultural qualities 

 and hence in their average crop yields to make it difficult to say 

 whether any difference manifest in 1914 was all or mainly due to 

 insect injury. To settle this point, I have taken the statistics of corn 

 production for these two sets of counties for the eight years from 

 1902 to 1909 inclusive — a period during which there was no chinch- 

 bug injury in any part of either area ; and I find that corn averaged 

 35 bushels per acre, during these years, in the counties which became 

 infested by chinch-bugs in 1914, and 32 bushels per acre in those 

 which were uninfested in that year. This difference of three bush- 

 els per acre being in favor of the infested area, it is evident that this 

 area is at least as productive, under ordinary conditions, as the other. 



The year 1914 was one of severe and destructive drouth in central 

 and southern Illinois ; and it seemed possible that the two sets of 

 counties selected might have differed with respect to the degree of 

 drouth in a way to add a greater weather injury to that done by 

 chinch-bugs, and thus to make it impossible to tell just how much was 

 due to the latter alone. Reference to the published reports of the 

 U. S. Weather Service, gave me nineteen points in the infested area 

 at which the weather of the season was recorded, and seventeen such 

 points in the uninfested area. It is generally agreed that the weather 

 of June, July, and August makes the corn crop, that of August being 

 the most important ; and I consequently brought into comparison the 

 rainfall and temperature of the two areas for these months, with the 

 result that the total rainfall during these months for the infested 

 counties was found to be 8.07 inches, and that for the uninfested 

 counties 7.85 inches — a difference of only .22 of an inch in the three 

 months, which is too small a deficiency to have any significance in this 

 comparison. Moreover, an examination of the monthly means of rain- 

 fall for the separate months shows that the deficiency in the infested 

 counties was most marked in June, when it would have had the least 

 effect upon the corn crop, and least so in July, and that in August, the 

 most important month for the growth of corn, the rainfall was larger 

 by nearly two thirds of an inch in the infested area than in the un- 

 infested. 



