59 



weather are greatest in the southern portion of the State. But the dif- 

 ference between this weather condition is certainly not so marked be- 

 tween Tippecanoe and Benton Counties on the one hand, and La Porte 

 and Lagrange Counties on the other, as to result in a difference in the 

 number of bugs amounting to that between a great abundance and 

 almost none at all. In Tables E, F, and G are given the mean tempera- 

 ture and rain-fall for the months during which these elements most 

 affect the Chinch Bug, and extending over a period of five years.* This is 

 as far back as the Indiana records extend. The records from Princeton, 

 Ind., indicate the meterological conditions during this period in the bug 

 infested area, and those from Angola are a like record of the weather 

 conditions in the region exempt from Chinch Bug attack, while Table G 

 gives the meterological conditions in De Kalb County, northern Illinois, 

 where Chinch Bugs have been abundant since 1855, formerly doing serious 

 damage to spring wheat, and have, since about 1862 (wheat of any sort 

 being no longer grown to any extent), been transferring their attention 

 to the corn crop, but being at present less abundant than in south- 

 eastern Indiana or southern Illinois. 



From a study of the tables given it will be seen that while the 

 northern Illinois locality had a less rain-fall during the spring and early 

 summer than the northern portion of Indiana, it also had a less amount 

 than had southern Indiana; yet, while Chinch Bugs are more numerous 

 in the Illinois section than in northern Indiana, they are not so abund- 

 ant as in southern Indiana. 



Geologically, the northern portion of Indiana differs from the south- 

 eastern portion, the former being Devonian and the latter carbonifer- 

 ous or subcarboniferous. This, however, could have little effect on the 

 Chinch Bug, except, possibly, so far as it influenced the natural flora, 

 especially the grasses. Prof. James Troop, who has made the grasses 

 of Indiana a study, informs me that the following are all, or nearly all, 

 the species found in the southern portion of the State which do not 

 occur in the northern portion : Uniola latifolia, Arundinaria tecta, Pas- 

 palum fluitanSj P. Iceve, Panicum prolificum, P, anceps, P. vicidum, Andro- 

 pogon divisitiflorus. 



From the foregoing it will be seen that to no one of these elements 

 alone, as existing between southwestern Indiana and Illinois on the 

 one hand, and northeastern Indiana, south eru Michigan, and northern 

 Ohio on the other, can this immunity from Chinch Bugs in these last 

 localities be traced. Whether the combination of two of these elements, 

 such as dry weather and wheat- growing, is to be held wholly responsi- 

 ble, or whether there is still another potent element, as yet unknown 

 to us, which, either in itself or combined with some other, is the prime 

 cause of the present state of affairs, only future studies can demonstrate. 



* Kindly supplied me by N. E, Ballon, M. D., Ph. D., Sandwich, 111., for thirty years 

 volunteer signal observer at that place. — F. M. W. 



