THE EUROPEAN CORN BORER AND ITS CONTROL. 45 



larval instars. During this, or the succeeding instars, the larva; sometimes 

 wander about and do their greatest amount of damage to the plant. Some 

 individuals leave the terminal internode and tunnel through the lower 

 parts of the stalk; some tunnel from the terminal internode down through 

 the intervening nodes into the lower part of the stalk; while others enter 

 the stalk at various places along its length and tunnel upward or down- 

 ward according to their individual preference. The junction of the leaf 

 sheath and node is a favorite point of entrance, although this is by no 

 means universal. Frequently the larv^a enters a stalk and tunnels out 

 a cavity, only to abandon it and enter the plant at a different point. The 

 stalk may be tunneled by the larva? to its base, or even into the taproot, 

 so that corn stubble is often infested and must be considered a source 

 of danger in clean-up operations. 



During their wanderings the larger larvae very often descend the plant 

 until they reach the side branch, or pedicel, on which the ear is borne. 

 Here they may enter the main stalk or may enter the pedicel and tunnel 

 into the ear. Some enter the ear directly by boring through the husk, 

 later feeding on the immature kernels or tunneling through the cob. In 

 other instances the ear is entered at the tip end, and the larvae tunnel 

 through the kernels and the cob. Apparently the ear is very much 

 favored as a food by the larvae. 



In instances when the fifth instar larvae molt into the sixth, seventh 

 or eighth instars (see Table III), the molting process takes place in the 

 same manner and location as has been described for the fourth to fifth 

 instar molt. 



The habits of the larvae vary greatly with different individuals and 

 under different environments. For this reason the preceding remarks 

 are intended to give only an idea of their usual activities in this stage, 

 and their habits when attacking corn. In general, it may be stated that 

 they may attack all parts of the corn plant except the fibrous roots, and 

 that this damage may occur in an indefinite number of ways by larvae of 

 the different instars. 



Second Generation. 



When attacking corn the habits of the second generation larvae are 

 essentially the same as have been described for those of the first generation. 



The only exception is that a large proportion of the larvae hatch from 

 eggs which have been deposited directly upon the silk or husk of the 

 immature ears. They feed first upon the tender leaves of the husk, and 

 upon the silk, and then tunnel through all parts of the ear. This type 

 of injury is of great economic importance, especially in sweet corn or that 

 grown for seed. The amount of damage to corn by larvae of the second 

 generation is, therefore, infinitelj^ greater than that caused by those of 

 the first generation, due to the greater numbers of the second generation 

 and their habit of attacking the ears directlj'. 



The nearly full-grown lai-vae winter over within their tunnels in the 



