THE EUROPEAN CORN BORER AND ITS CONTROL. 47 



be distinguished from those not infested, as the terminal stalk withers 

 and droops above the point where the small, first instar larva entered. 

 After entering the stalk it tunnels downward, molting within the tunnel , 

 as it develops in size. This tmmel is not continuous, owing to the fact 

 that the larva emerges from the stalk at will, and enters again at a point 

 nearer the base. It usually tunnels exclusivelj' in the internodes of this 

 plant, very rarely passing through a node. In tliis particular the habits 

 of the larva, when attacking lady's-thumb, are distinctive because the 

 node is commonly tunneled in other plants. 



Habits whex attacking Barnyard Grass. 



The habits of the European corn borer larvje, when attacking barnyard 

 grass, are verj^ similar to those that have been detailed in the injury to 

 dock, except that the larger ones, instead of continuing to feed on their 

 original host, often leave the stalks of barnyard grass, where they have 

 partially completed their development, and enter others. 



Barnyard grass commonly serves as a host for the second generation 

 larv'jB until the middle of October. At this time it becomes dry and 

 hard, and many of the larvge desert it for more attractive food plants 

 groM^ng in the vicinity, though a large percentage of the original number 

 present continue feeding in the lower parts of the plant, and may be 

 found inside the base of the stalk, below the level of the ground, as late 

 as November 30. It is believed that the nearly full-grown larv^se pass 

 the winter in this location, although complete data on this point will be 

 lacking until observations are made in the spring of 1919. 



Superficial observers have frequently stated that barnyard grass is 

 entirely deserted by larvae of the European corn borer during the late 

 fall season, but close examination will reveal many at the bases of the 

 stalk. In this position they are yerry difficult to destroy by ordinary 

 clean-up methods. 



Molting. 



Wlien feeding on, or near, the surface of its food plant, especially during 

 the early instars, the larva spins a molting cocoon within which it molts. 

 This is formed of thin, silken strands, and is located in any protected 

 place. WTien tunneling inside its food plant the larva does not form a 

 molting cocoon, but merely closes the entrance to the tunnel with a thin, 

 silken partition. It then molts inside this tunnel near its last feeding 

 place. 



The process of molting varies in detail with the different instars, but 

 in general is as follows. After all preparations to secure protection have 

 been made, the larva enters a semi-quiescent state during which the head 

 capsule becomes pushed forward uiitil a distinct non-contractile, white 

 band appears between the head and the shield. After remaining in this 

 condition approximately twelve to twenty-four hours the old larval skin 

 splits longitudinally just back of the head capsule, and, as a result of 



