86 



in 1910 makes it very likely that infestation actually began over much 

 of this area of injury in 1909, and farther on in tracing the relations 

 of the outbreak to prevailing crops I have assumed that this was the 

 fact. 



How little a deficient rainfall can have had to do with the com- 

 mencement of this outbreak is shown by the fact that there was no 

 dry summer in this district during these years until 1911, that of 

 1909 being virtually normal as to rainfall, and May to August in 

 1907, 1908, and 1910 being decidedly wet in Randolph county, with 

 an excess of rainfall varying from 3% to Sy 2 inches for each of these 

 three years. 



At this point the inquiry will naturally arise whether there were 

 not other places in southern Illinois where the spring and summer 

 weather of these years was equally favorable to a rapid multiplication 

 of the chinch-bug, but where nothing of the sort actually occurred. 

 As an answer to this question I have prepared the following table 

 comparing temperatures and rainfall at the southern Illinois stations 

 in 1908 and 1909. From this it will be seen that both Flora and Cob- 

 den, in Clay and Union counties, show conditions quite as favorable 

 to the chinch-bug as those at Tilden, in that the breeding months 

 were warm and dry at both the former in 1908, and warm at both in 

 1909 with a rainfall a little below the normal at Flora and less than 

 an inch above the normal at Cobden. 



Departure from Normal Temperature and Rainfall, Southern Illinois Sta- 

 tions, May to August, 1908-09 





1908 



1909 



Weather stations 



Temperature, 

 degrees 



Eain, 

 inches 



Temperature, \ Eain, 

 degrees inches 



Albion 



Cobden 



+2.6 

 +1.4 

 +5.5 

 —3.4 

 0.0 

 +4.0 

 +1.9 

 —2.9 

 +5.1 



—2.96 

 —3.50 

 —3.50 

 +4.91 

 —2.45 

 —1.88 

 —1.37 

 —0.04 

 +3.17 



^0.6 

 +4.5 

 +3.8 

 +0.5 

 +1.5 

 +1.8 

 —1.3 

 +2.7 

 +4.2 



+0.57 

 +0.86 

 —0.18 

 — 0.64 



Flora , 



Greenville 



McLeansboro 



Mt. Vernon 



—1.21 

 +0.65 

 +1.31 

 —0.35 

 —0.26 



Olney 



St. John 



Tilden 







Evidently there must have been something other than the weather 

 of these two years to prevent the appearance of destructive numbers 

 of the chinch-bug in the districts around these two stations. It is 

 when we compare the three counties with regard to their agricultural 

 conditions, that we find differences having an important bearing on our 

 inquiry. 



Clay county differed from Washington county in 1909 especially 

 in the smaller percentage of its area in wheat (1 percent in Clay 

 county and 12.6 percent in Washington), and in the smaller area in 



