91 



Counties, Group B (subsequently infested) 



Jersey 

 Macoupin. . 

 Madison. . . 

 Montgomer 



Totals. 



Wheat 



Oats 



Corn 



17,827 

 23,844 

 65,100 

 37,275 

 144,046 



860 



10,427 



6,047 



22,712 



40,046 



34,286 

 41,280 

 69,122 

 70,383 

 215,071 



Forage 

 19,968 

 51,173 



70,029 



80,707 



221,877 



Acreage in above crops: 



Group A, 287,766 acres 



Group B, 621,040 " 

 Cultivated area, 1911: 



Group A, 837,749 acres 



Group B, 1,036,956 " 

 Azzrcounties north of infested area of 1911; infested in 1912. 

 B— counties southeast of infested area of 1911; not infested in 1912. 



Crop Eatios, 1911 (Ratio of Area in each Crop to Total Area under 

 Cultivation) 



Group 



Wheat 



Oats 



Corn 



Forage 



3.86% 

 13.9 % 



3.71% 



3.8 % 



11.3% 



20.8% 



15.4% 

 21.4% 



From this table we see that the area in chinch-bug erops was 

 much smaller in Group A (34.3 percent) than in Group B (59.9 per- 

 cent), and that the ratio of wheat in Group B was three and a half 

 times as great as in Group A. In other words, the outbreak extended 

 from the area infested in 1911 northward over country planted largely 

 to cereals and grasses, and with a high ratio of wheat, but did not 

 spread over counties to the east and southeast with a smaller area in 

 these chinch-bug crops and a materially smaller one in wheat. 



Another reason appears, however, for this rapid northward spread 

 of the chinch-bug outbreak, in a fact brought especially to my atten- 

 tion by one of my field assistants, Mr. W. P. Flint. The principal 

 chinch-bug nights — the dispersal flights — are those which carry the 

 insect over new territory in spring when it emerges from its winter 

 quarters, in midsummer when the first generation reaches maturity, 

 and in fall when the insect leaves the' fields in search of winter quar- 

 ters. The principal spring and fall flights are especially lfkely to 

 occur upon warm days following upon raw and chilly ones, conditions 

 under which the prevailing winds are from the south. 



This fact is illustrated by the following data of the direction and 

 velocity of the wind at Springfield at times when our field notes show 

 the occurrences of considerable flights of chinch-bugs in the infested 

 area. 



