THE LESSER CORN STALK-BORER. 17 



DURATION OF THE MOLTING PERIOD. 



During the summer months the time required for the larvae to molt 

 varies from 12 to 24 hours in all the instars and during the fall from 

 12 to 26 hours and sometimes 48 hours. The majority of the larvae 

 in fall require only 24 hours. Generally a longer time is required in 

 the last instars than in the first ones. 



DESCRIPTION OF ECDYSIS. 



The larva when about to cast its skin becomes pale, sluggish, and 

 usually remains motionless in tunnel or tube unless disturbed, and 

 even then it is not as active as normally. The first real indication 

 that molting has commenced is the appearance of a pale whitish 

 patch in the region of the neck. This patch is the outer conjunctival , 

 layer which, having been loosened, is being unfolded to accommodate 

 the growing larva. This patch becomes more and more evident as 

 molting progresses. The eyes at this time can be seen through the 

 semi transparent conjunctival layer, appearing a little distance back 

 of the head mask. The outer layer of the cuticle, having been loos- 

 ened throughout, ruptures immediately back of the head mask, 

 first on the venter, then rapidly extending laterally and dorsally. 

 The larva with wavelike rhythmic motions gradually draws itself out 

 of the old cuticular layer. Just at the point when the last joint is 

 being extricated the larva bears down with the head and frees itself 

 from the mask. 



FEEDING HABITS OF THE LARVA. 



The larva of the species, as its common name would indicate, has 

 a habit of boring or tunneling into the stems of growing plants (PI. 

 Ill, fig. 3) and feeding within. This manner of feeding is especially 

 characteristic where young corn and sorghum plants are attacked. 

 The larvae in such cases tunnel into the stalks at or slightly below 

 the surface of the ground, through and sometimes up the heart for 

 a distance varying from 1 to 2 inches. The bud leaves of such af- 

 fected plants die, having been severed from the main plant; Plate 

 III, figure 2, shows the appearance of such a plant. The bud leaves 

 dry up and wither away. Some of the plants may survive, but 

 such plants remain in a dwarfed condition or become deformed and 

 one sided. 



Injury to corn in this manner resembles closely the work of the 

 southern corn rootworm (Diabrotica 12-punctata Oliv.); however, 

 E. lignosellus is an upland species, being found only in the driest 

 of soils, while the corn rootworm breeds generally in the moist 

 lowlands. 



In older corn and sorghum, as well as in cowpeas, the damage con- 

 sists primarily in the girdling of the stems at or slightly below the 

 surface of the ground, but the larvae also tunnel into the stems, 



