122 



FIRST BOOK OF FORESTRY 



only effective way of fighting them is by cutting a number 

 of " trap trees." This is best done by girdling or felling 

 a number of the smaller, poorer trees, about fifty yards 



FIG. 46. Bark Beetles and their Work 



A, Galleries on a block of wood, just beneath the bark ; B, the bark beetle Tomicus ; 

 C, the bark beetle Dendroctonus. Natural size is indicated by straight line 

 between beetles 



