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ON AN OUTBEEAK OF INJURIOUS LOCUSTS IN 
CENTRAL ILLINOIS. 
BY CLARENCE M. WEED. 
In an article published as one of the series of “Miscellaneous 
Essays on Economic Entomology,”* issued from this office last] 
year, the writer recorded a few of the more important facts con- : 
cermng an outbreak of two common locusts—the red-legged lo 
oust (Pezoiettix femur-rubrum), and the olive locust (P. differen-, 
looc 7^ hlch ° ccurred in Central Illinois during the summer of 
. 4 , 1 have U iere reported the approximate boundaries of the 
infested aiea, the extent of injury within that area, and such ob- : 
servations as I had been able to make upon the situation and 
o? n it • the l0CUS ^ . eggs at tlie beginning of the winter of 
Ibbo-bb It is proposed m the present paper to bring the record 
up to the autumn of 1886, when the observations ceased, and to 
present a few general considerations which it is hoped may form 
tion Ul COntnbutiou to tlie sub i ect of entomological prognostica- 
In the paper above cited I have shown that a considerable pro¬ 
portion of the eggs had been destroyed by various insect and 
other enemies during the autumn of 1885,—the most useful of 
these enemies being the larvae of the ground beetles (Carabidse), 
and those of the blister-beetles (Meloidse). Late in March, 1886 
the region was again visited, and extended observations were made 
upon the condition of the eggs. The meloid larvae were present 
though in the quiescent coarctate condition in which they pass 
the winter; but many of the carabid larvae had already begun to. 
work upon the eggs. The most remarkable feature of the situa¬ 
tion, however, was the extraordinary abundance of the red locust 
mite (Trombidium locusfavwn ) which was everywhere present on 
and beneath the soil surface. At French Grove, March 22, these 
mites were just beginning to come out of the ground; and in 
many pastures from one to four of them could be seen on every 
square foot of surface. By the roadsides they also swarmed. At 
Monica, on the. farm of Mr. W. E. Elliot, thirteen of the mites 
were counted within a surface area of one square foot. 
*Rep. Ill. St. Bd. Agr. 1885, appendix, pp. 48-66. 
