48 
The Locust Borer 
(Cyllcne robmice Forst.) 
A great obstacle to the growth of the common black locust as 
a timber tree in Illinois has been the work of a borer which in- 
fests this tree only, multiplying year after year in a locust grove 
until it destroys every tree. It was a common practice in the early 
settlement of the northern part of the state for the farmers to plant 
a grove of locusts, with a view especially to a supply of fence-posts. 
These groves were, however, all destroyed by this borer during the 
middle part of the nineteenth century, and the planting of this 
tree was universally abandoned at that time. Of course, with the 
disappearance of the tree the borer likewise disappeared, and the 
growing of the locust is now again possible if due precautions be 
taken against its destruction by this insect. Fortunately, the recent 
work of Dr. A. D. Hopkins, in charge of forest insect investigations 
for the United States Department of Agriculture, has made it per- 
fectly feasible to grow locusts with little or no loss from this cause, 
and the following account is mainly taken from his publications on 
this subject. 
The first evidence of attack by this borer in spring is a fine 
brownish dust and an oozing of sap from the bark. Later, gumlike 
exudations appear on the injured spots, and quantities of yellowish 
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Fig. 54. Locust Borer. Cyllene robinice, pupa: a, front view; 
6, back view. Enlarged as indicated. (U. S. Dept. of Agri- 
culture.) 
