AETIFICIAL 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 overcame 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. 
