228 MANUAL OF VEGETABLE-GARDEN INSECTS , 

 The Larger Corn Stalk-Borer 



Diatrcca zeacolella Dyar 



In the southern states nortliwanl to Kansas and Maryland, 

 corn is sometimes attacked by a whitish caterpilhir marked with 

 dark brown spots. This insect is closely related to the sugar- 

 cane borer and until recently the two have been considered the 

 same. These caterpillars bore into the stalks of young corn, 

 causing the plants to become dwarfed and distorted. They 

 often bore through the unopened leaves, producing groups 

 of small holes symmetrically arranged on the two halves of the 

 expanded leaf. The larvae of the second generation burrow into 

 the stalks below the second or third joint, weakening them so 

 that the plants are easily blown over by the wind. The insect 

 hibernates as a full-grown larva in a burrow in the tap-root 

 below the surface of the ground. Pupation takes place in the 

 spring within the burrow and the moths emerge in ten days or 

 more. The straw-yellow moth, with an expanse of 1 to 1| 

 inches, lays her eggs in clusters of two to twenty-five, either on 

 the lower or more rarely on the upper side of the leaves of the 

 young corn. The egg when first laid is creamy white, gradually 

 changing to orange-brown, flattened, oval, slightly convex 

 and about -^ inch in length. In the cluster the eggs overlap 

 and are usually arranged in two, three or four rows. The egg 

 hatches in a week to ten days and the young caterpillars at first 

 feed on the upper leafy part of the young plant but soon bore 

 down into the stalk. There is considerable migration of the 

 caterpillars from plant to plant and a borer may leave the 

 stalk at one place only to re-enter at another point. The 

 caterpillars mature in twenty to thirty days. The full-grown 

 larva is about an inch in length, dirty white, usually marked 

 with numerous dark brown spots. When about to pupate, the 

 caterpillar cuts through the stalk an exit hole for the moth 



