120 



FIRST BOOK OF FORESTRY 



a 



away from the gallery of the mother beetle, and thus the 

 many little parallel galleries and odd patterns seen in the 

 figure are produced by this one family. After a few 

 weeks the grub, or larva, wraps itself up in the wood dust 

 made by its tunneling, and about three weeks later has 



changed into a beetle. This 

 beetle may bore out at once 

 and hunt another tree and 

 thus repeat the cycle, so that 

 a second or, in some cases, 

 even a third brood is produced 

 during the same season. 



Examining the figure, it is 

 evident that, if many such 

 families lived in this same 

 branch, the branch would be fairly girdled ; each little 

 gallery would hinder the water from going up, and also 

 hinder the food made by the leaves from coming down, 

 and the effect would be exactly as if the bark were stripped 

 and the tree girdled. As soon as these beetles appear in 

 large numbers, so that a hundred and more occur on every 

 square foot of the trunk, the tree is doomed. It is generally 

 believed that these beetles prefer sickly or dying trees ; but 

 it is certain that when once they are very numerous they 

 readily attack sound as well as injured trees. 



Some bark beetles occur in our woods at all times ; but 

 it is only when then- enemies are asleep, and when numerous 



FIG. 44. Pine Weevil: Adult 



Beetle, Pupa, and Grub, 



or Larva (enlarged) 



(After Packard) 



