n 



The hardwoods are also warred upon by bugs, 

 weevils, borers, and fungi. The percentage of 

 swift deaths, however, that the insects cause 

 among the hardwoods is much smaller than 

 that among the pines ; but the percentage of 

 diseased and slow-dying hardwoods is much 

 greater. The methods of beetles that attack 

 oaks, hickories, aspens, and birches are simi- 

 lar to the methods of those that attack pines 

 and spruces. They attack in swarms, bore 

 through the bark, and deposit their eggs either 

 in the inner bark or in the cambium, the 

 vitals of the tree. The grubs, on hatching, begin 

 to feed upon the tree's vitals. In this feeding 

 each grub commonly drives a minute tunnel 

 from one to several inches in length. Where 

 scores of grubs hatch side by side they drive a 

 score of closely parallel tunnels. Commonly 

 these are either horizontal or vertical and gener- 

 ally they are numerous enough to make many 

 complete girdles around the tree. Girdling 

 means cutting off the circulation, and this pro- 

 duces quick death. 



While these beetles are busy killing unnum- 

 181 



