SOME ENEMIES OF THE TREES io«? 



The many bark beetles wMch are so destruc- 

 tive to shade and forest trees are borers. Let 

 us see how they work. In the spring, the young 

 beetles pair and fly off in search of a home, pref- 

 erably an old injured tree of large dimensions. 

 Here the female beetle at once sets to work to 

 bore a passage or gallery, partly in the bark 

 and partly in the firm wood -beneath. She lines 

 both sides of this snug nursery with eggs, 

 usually froia fifty to one hundred in number. 

 When the eggs hatch, the tiny grubs begin to 

 bore toward the outer world, running a host of 

 little parallel galleries which form all sorts of 

 odd-shaped patterns and work no end of havoc 

 in the tree's sap passages — ^for each little gal- 

 lery hinders the upward trend of the crude ma- 

 terial, and also delays the return of the manu- 

 factured product. After a few weeks, the grubs 

 roll themselves in the wood dust they have 

 bored, and are transformed into beetles in three 

 weeks' time. Then they finish tunneling their 

 way out, mate and fly off, and thus repeat the 

 cycle, so that a second, and sometimes a third 

 generation is produced the same season. If it 

 happens that the beetle mother takes up her 

 abode on a branch, the chances are that it will 

 be girdled by the little galleries and so killed. 

 If the mother chooses a place on the trunk, and 



