INSECTS INJURIOUS TO SWEET CORN 



203 



course of its lifetime. When full fed it penetrates to the outer 

 surface of the stalk and makes a hole from which in due 

 time it issues as a moth. Figure 129, a. shows a stalk infested 

 by the first generation of borers, and b a stalk cut open to 

 show the larval burrow in which the pupa is resting. The 



Fig. 129.— (7, Stalk infested by first generation of borers; b, stalk cut open (redrawn) 



pupa state is assumed in Virginia from the middle of July on, 

 and the moths issue ten days to two weeks later. The eggs 

 for the second generation are deposited soon afterwards on 

 higher grown stalks, and the larvae are mature by harvest time. 

 The injury accomplished by the second generation consists 

 largely in the weakening of the stalk so that it is readily blown 

 down by winds, whereas damage by the earlier generation pre- 



