ENEMIES OF PLANTS. 



333 



base of the trunk, under a loose scale of the 

 bark or in a little incision made by the mandibles. 

 In about two weeks the larva is hatched, and at 

 once begins to gnaw into the sapwood and inner 

 bark, where it remains for a year, making "disc- 

 shaped mines," in the lower part of which it 



FIG. 121. ROUND-HEADED APPLE-BORER (Saperda Candida, Fab.). 

 (After Division of Entomology, United States Department of Agriculture.) 



spends the winter. The following summer it 

 again works in the sapwood, and in the third 

 season " cuts a cylindrical passage upward into 

 the solid wood " (Fig. 122). It afterward gnaws 

 out toward the bark, sometimes going on through 

 the tree.* "It changes to a pupa Q r ) near the 

 upper end of its burrow in May, and emerges as 

 a beetle in June." 



(2) PREVENTIVES. Nature furnishes many 



Comstock's Manual for t/m Study of Insects, p. 573. 



