THE POPLAR AND WILLOW BORER 



467 



earlier, but from numerous examinations made during October the major- 

 ity of the eggs had not hatched even as late as October 28. Early in 

 November, 1915, the eggs began hatching in great 

 numbers, and this continued until the latter part 

 of the month. 



Tlie larva 



When hatched, the young larva (fig. 116) is 

 whitish in color and greatly resembles a miniature 

 June-beetle grub except that the posterior end is 

 the smaller and the larva is legless. It lies curled 

 up in the egg cavity and begins at once to feed 

 on the soft plant tissues. It is 1.5 millimeters in 

 length, and 0.6 millimeter thick at its widest part. FIG. 116. YOUNG LARVA, 



T^ 11 1 1 i j v , 1. 1 JUST HATCHED 



It is regularly transversely wrinkled, but the skin 



is nearly smooth except for scattering fine 

 hairs. The head and the mouth parts are 

 light brown except the mandibles, which are 

 dark brown with black tips. The larva is 

 cylindrical in shape, gradually tapering 

 toward the posterior extremity. 



The larva feeds on the tender tissues of 

 the plant and soon reaches the soft cambium 

 layer. Externally the beginning of feeding can 

 be easily recognized by the blackish, wet frass 

 that fills the outer part of the egg cavity. 

 Feeding continues until cold weather, the 

 early-hatching larvae attaining a considerable 

 growth. 



In the spring feeding begins as soon as the 

 weather has become sufficiently warm, usually 

 the first week in April. Moist frass, black to 

 brownish in color, is forced out of the burrow 

 as the larva feeds ravenously. The direction 

 of the larval channels is nearly always around 

 the trunk or the branch, and the larvae feed 

 at first exclusively in the bark and the cam- 

 bium layer. As a result the tree is frequently 

 girdled, especially if several larvae are at work 

 near the same place (fig. 117). The larval 

 channels vary greatly in shape; some are 

 cylindrical and girdle the tree, others are flat, irregularly shaped chambers, 

 while the majority zigzag in various directions through the cambium layer. 



FlG. 117. CHANNELS MADE BY 

 LARV.E IN A YOUNG CARO- 

 LINA POPLAR TREE 



