96 



slower and less effective agencies had been for some time at work in 

 the same direction, one of them at a rapidly increasing rate. There 

 was no notable development of fungous disease such as has sometimes 

 been useful in hastening the disappearance of an unusually injurious 

 outbreak, but there was a considerable number of predaceous insects 

 which found in the chinch-bug horde an acceptable and convenient 

 food supply ; and a minute insect parasite of the eggs of the chinch- 

 bug had appeared in the fields and begun to multiply much more rap- 

 idly than the chinch-bugs themselves — at a rate, indeed, to check se- 

 verely or perhaps to suppress entirely the uprising within a year or 

 two longer. 



Effect of Predaceous Inserts. — My field assistant.. Mr. W. P. Flint. 

 reports a list of some twenty species of predaceous insects — mostly 

 lady-beetles, ground beetles, bugs (Hemiptera), and larvae of lace- 

 wing flies — which were eating chinch-bugs in the fields searched by 

 him. By carefully collecting and counting chinch-bugs and their in- 

 sect enemies in twenty-six separately measured square yards of wheat 

 stubble in different parts of central Illinois, he found that the num- 

 ber of these predaceous insects to that of the chinch-bugs in these 

 fields in July, was about as 1 to 17 ; and by insectary experiments in 

 feeding the various species of these insect enemies with living chinch- 

 bugs, he further found that the predaceous insects occurring on an 

 average square yard of stubble would eat 11 chinch-bugs a day if 

 confined to them for food. This is equivalent to about a million a day 

 in a 20-acre field— a number much too small to have any marked ef- 

 fect upon a serious infestation. 



In addition to the foregoing I have an interesting note of an ob- 

 servation made June 16, 1914, by Mr. P. A. Glenn, of my office staff. 

 While observing chinch-bugs in a Sangamon county .corn-field he no- 

 ticed that ants (Formica fusca sxibsericea) which had their burrows 

 in corn hills were attacking and killing many of the chinch-bugs that 

 came near the corn, the ground around the hill being thickly strewn 

 with the dead bodies of the bugs. The hill of corn which the ants were 

 defending was in a healthy condition and comparatively free from 

 the bugs, while the hills around it were covered with chinch-bugs, 

 many of them killed. Numerous other hills of corn in the part of the 

 field overrun with chinch-bugs were being similarly defended by the 

 ants. 



Mr. Flint also reports a similar habit of the common corn-field ant 

 [Lasius niger americanus) . When spraying corn with Black Leaf 40. 

 he twice saw this ant capture and drag away stupefied chinch-bugs; 

 and he found the remains of 27 adult chinch-bugs in one of its nests. 



Effect of tlie Egg Parasite. — An egg parasite of the chinch-bug 

 {Eumicrosoma benefica Gahan) discovered by McColloch in Kansas 

 in 1913* was first found in Illinois Januarv 14. 1914. hibernating 



■Canadian Entomologist, Vol. 45, p. 342. 



