ARTIFICIAL INTRODUCTION OF PARASITES. 143 



on his own initiative, conducted two separate experiments, thus 

 rendering the results twice as valuable. 



April 18 a minor introduction of parasites was made at McPherson, 

 Kans., and on April 21 there was another similar one at Sterling, 

 Kans. Parasitized " green bugs " were observed present at each place 

 on these dates. 



Mr. Ainslie remained in the vicinity of Wellington, and more briefly 

 at McPherson and Sterling, for the purpose of making accurate obser- 

 vations on the effect of these introductions. 



Two weeks later, on visiting the two fields at Wellington, where 

 the first introduction had been made, Mr. Ainslie found that on 

 account of the cold weather the effect upon the parasites was almost 

 the same as though they had been kept in cold storage. Some of 

 those sheltered by the box lids had issued, but had apparently not 

 ventured far from their shelter and were found in a semitorpid condi- 

 tion capable of little movement. The percentage of parasitism from 

 Aphidius appeared to be the same in all other fields in this locality, 

 irrespective of these introductions, except close about the box lids, 

 where they seemed a little more numerous, the conditions of para- 

 sitization generally being about the same as had existed two weeks 

 previous. The Toxoptera, however, had greatly increased in num- 

 bers, and the fields were now plainly showing the effects of their work. 



Subsequent examinations of fields at Wellington showed that after 

 the weather warmed up in May the parasites speedily overcarne the 

 Toxoptera and that the fields where these artificial introductions 

 were made had suffered as much as any fields in the neighborhood 

 from attack by the "green bug." All of this seems to indicate that 

 no noticeable good resulted from these introductions, which, in the 

 light of our present knowledge, is not at all surprising. The minor 

 experiment at McPherson was also reported upon to us by Mr. W. 

 Knaus, and his report was in accord with our own observations. 



On May 17 an artificial introduction of parasites was begun at 

 Manhattan, Kans. 1 While this experiment bore out our former 

 observations, the results obtained here should not bear as much 

 weight as the earlier introductions, since the Toxoptera was already 

 nearly overcome when the introduction was begun. 



When one stops to consider the numerous and varied hosts of 

 Aphidius testaceipes, its manner of hibernation, its wide distribution, 

 and the higher temperature required for its development over and 

 above that needed by its host ; also the fact that it may readily be 

 transported along with its host as adults, or within the body of the 

 latter, one can readily see the futility of attempting materially to 

 increase its numbers or efficiency by artificial introduction into 

 grain fields. 



i Cir. 93, Bur. Ent. U. S. Dept. Agr., pp. 10-12, Aug. 22, 1907; Cir. 93, revised, Bur. Ent., U. S. Dept. 

 Agr., pp. 12-13, June 23, 1909. 



