def 
acres. In one of these it was determined to introduce enormous 
numbers of parasites artificially, keeping records of this field for 
comparison with the other field in which no introductions were made. 
thus determining the measure of benefit, if any, which resulted from 
the artificial introduction. Mr. Ainslie was instructed by wire to ship 
from Wellington, Kans., 6 bushels of the wheat plants that had been 
Stalk of wheat, the leaves covered with dead ‘“‘ green bugs” killed by the parasite 
Lysiphlebus tritici. About natural size- (original). 
Fie. 5. 
destroyed by the “ green bug ” and which, in some cases, were literally 
covered with the parasitized bodies of the pest, upward of 500 having 
been found on a single plant (see fig.5). Before taking up the experi- 
ment, however, it was desirable to know just what the conditions were 
under which it was begun. As stated above, one of these oat fields was 
used for the experiment of introducing parasites, while the other was 
kept as a check. The fields were so widely separated that the intro- 
[Cir. 93] 
