97 



among corn-field grasses in Macoupin, county, and again in a similar 

 situation March 3, near Marissa, in St. Clair county. Other speci- 

 mens were obtained June 24 by keeping in closed dishes chinch-bugs' 

 eggs collected May 5 at Plainview, in Macoupin county, and again 

 August 6 from eggs collected June 10. The extent of parasitism thus 

 disclosed was, however, very small. From 11,521 eggs obtained be- 

 tween May 7 and September 9 at various points in twenty-four coun- 

 ties, and kept under normal conditions, parasites emerged from only 

 140. 9 others dying, however, in parasitized eggs without completing 

 their transformations. In other words, only about 1.5 percent of all 

 the eggs collected during this period were found parasitized. Never- 

 theless, at some of the points where the presence of the parasites was 

 demonstrated in the fields, from a fourth to a third of the eggs were 

 parasitized, and the general average of parasites at nine such points 

 in six counties was 4.2 percent (149 parasites to 3524 eggs). In Kan- 

 sas during this same year the percentage of egg parasites at Man- 

 hattan varied from .016 of 1 percent in May to 9 percent in August, 

 and 25 percent in September, the last ratio being based, however, on 

 a very small number of eggs collected. The ratio for the 11,000 eggs 

 obtained at that place during the season was 15 percent parasitized, 

 instead of the 1.5 percent in Illinois. In sixteen Kansas localities from 

 which eggs were gathered in July and August, 1914, the percentage of 

 parasitism was 14.5, while in Illinois the ratio for 1356 eggs collected 

 in the same months in twenty-two localities was 10.6 percent. 



The chinch-bug egg parasite had evidently made an excellent start 

 in Illinois in 1914, materially helped on by our importation of para- 

 sitized eggs from Kansas, when the weather intervened to destroy in 

 great measure both the chinch-bugs and the parasites of their eggs. 

 The following year (1915), parasitized eggs of chinch-bugs were found 

 in fifteen Illinois counties instead of the six of the year preceding, 

 but only 1.3 percent of the eggs collected in April. May. and June at 

 these places were parasitized (128 parasites to 9972 eggs). It seems 

 probable that the minute and delicate-winged parasites were even 

 more susceptible to injury and destruction by the stormy, drenching 

 weather of the season than were the chinch-bugs themselves. 



Artificial Measures of Control 



It is evident from the foregoing that the "natural enemies" of the 

 chinch-bug did it no serious harm in Illinois during the six years of its 

 destructive prevalence here, and it remains to see what was attempted, 

 what was done, what might have been done, and what may be done 

 hereafter in any similar case arising, by man, the arch-enemy of all 

 Ihe injurious insect species. Other so-called "enemies" of the chinch- 

 bug are really its friends, in the sense that they find it useful to them 



