231 



clearly the hibernatiou of bugs directly adjacent to the fields they iufest 

 later. The fact that certaiu fields almost identical in conditions where 

 stubble, corn stalks, and other rubbish were burned, were very free from 

 bugs, while others not burned were badly infested this season, is strong- 

 confirm ation of this view. 



In about 90 per cent of the infested fields examined the ground was 

 high and iu all cases had been extremely dry during the preceding fall 

 and spring. In about 80 per cent the fields were hilly and ridged, and 

 in most cases the damage was first apparent upon the higher portions 

 of the fields, the exceptions to this rule being iu the case of fields 

 which had evidently become infested from bugs hibernating in slough 

 grass or weeds occurring iu lower places, and it must be noted here 

 that even these places were comi^aratively dry during the twelve 

 months preceding the damage of the present season. The character 

 of the soil does not seem to have been of so much importance iu deter- 

 mining the distribution, as we find a nearly equal distribution of cases 

 between black loam, clay loam, and sandy soils; but on the whole the 

 soils most infested were rather light and friable soils, even the clay 

 soils, where abundant, being of a rather light and in some cases sandy 

 character. As to the distribution in the State with reference to crop 

 distribution, the counties most infested are those in which there has 

 been a pretty continuous growth of small grains — wheat, rye, and 

 barley — but, as will be seen by comparing the chinch-bug distribution 

 with crops by the annexed tables, the distribution, instead of being for 

 those counties where spring wheat was the special crop, are those in 

 which fall wheat or rye constitutes the special grain crops. 



The infested area runs across various geological formations from Silu- 

 rian to Carboniferous, and clearly bears no reference to soils in this 

 regard; but from the fact that this area is in large part covered with 

 glacial dejwsit the geological horizon is of little consequence. 



It may be noted that the principal centers of injury are the divides 

 and bluffy sections adjacent to the river valleys of the Des Moines, 

 Skunk, Iowa, Cedar, and Wapsipinicon rivers and also along the Mis. 

 sissippi. 



It will be noticed that practically all the damage occurring in the 

 southeast quarter of the State and reference to the table of crop sta- 

 tistics will show that the counties Decatur, Wayne, Appanoose, Monroe, 

 Mahaska, Keokuk, Jefferson, Henry, Des Moines, Van Buren, Lee, 

 Louisa, and Muscatine are the most important fall-wheat districts, 

 while for spring wheat and barley the northwest counties of the State, 

 especially Kossuth, Emmet, Dickinson, Osceola, Lyon, Sioux, O'Brien, 

 Clay, Palo Alto, Plymouth, Cherokee, Buena Vista, and some others are 

 the important spring- wheat districts, and in none of these were chinch 

 bugs present in sufficient numbers so that they were reported. It would 

 seem, therefore, that the popular idea that chinch bugs affect spring 

 wheat rather than fall wheat is due to the fact that their injuries are 



