THE OUTBKEAK OF 1890. 28 



cause of the failure of the oats crop recognized was the green louse. 

 Directly upon this point his statements were as follows: 



We never had a better prospect for oats until the green louse began its work. Some 

 fields were not attacked by the louse, though it infested surrounding fields. From the 

 fields not attacked by it there was a splendid yield of oats; while, of course, the other 

 fields yield scarcely anything. In every township there were a few fields that were 

 not attacked by the green louse and that made a good yield. The fact that those fields 

 not attacked by the green louse invariably made a good yield, while those that were 

 attacked made a poor yield, is proof that in this part of the State, at least, the green 

 louse was the prime cause of the failure. 



This feature of the apparent immunity of some fields from attack 

 while others adjacent were destroyed has since been observed again 

 and again, especially along the borders of a serious invasion, which 

 was precisely the stuation in western Illinois at the time indicated by 

 Mr. Stahl. In Indiana the senior author investigated the outbreak 

 personally, and while the pest was present as far north as Lafayette, 

 there was little if any damage from its attacks north of Indianapolis. 

 In the neighborhood of Franklin on June 25 many fields were badly 

 damaged, but the injury was much more severe to the southward 

 and at New Harmony, tad., on June 11, the oats crop was ruined. 

 The same was to be said of the country across the Wabash River in 

 Illinois. While both Toxoptera and Siphonophora were present 

 in most cases the former largely outnumbered the latter and there 

 was no difficulty in properly crediting the destruction to Toxoptera. 



The occurrence of this insect in southern Ohio was greatly obscured 

 owing to the fact that it was, as elsewhere, confused with MacrosipJium 

 granaria Buct. Clarence M. Weed, writing for the Ohio Farmer (see 

 issue of July 12, 1890), states that in Ohio the grain plant louse had 

 been reported from Pickaway, Clermont, Butler, and Franklin coun- 

 ties. It seems, however, that in Clermont County, according to Mr. 

 Ed. C. Ely, the plant lice were at work as early as May 30. 



In a later issue of the same paper, July 19, 1890, Hon. Abner L. 

 Frazer, of Clermont County, Ohio, stated that the aphidids were 

 very numerous in his fields on June 9. While it is impossible to say 

 with absolute certainty that all damage was due to Toxoptera, 

 nevertheless Waldo F. Brown, writing from Butler County 1 on 

 June 19, says: 



Oats are in a critical condition. The leaves have turned red. It has not the 

 appearance of rust, looking more like the firing of a plant in dry weather, and I should 

 not wonder if the crop proved a total failure. 



In both Illinois and Missouri the aphidid causing the damage was 

 termed the " Texas louse," and wherever a technical name for it 

 was used at all it was called SipTionopTiora avense, Fabr. Because 

 Toxoptera was at that time but little known, and owing to the 



i Country Gentleman, June 26, 1890, p. 506. 



