THE MAPLE BORER. 377 



The burrows, or mines, either extend under the bark or descend into 

 the wood towards the heart of the tree. Different trees are variously 

 attacked. Where the worms remain under the bark large pieces are 

 loosened and gradually fall off", leaving sometimes nearly one side of 

 the trunk bare. At the same time the general health of the tree is 

 impaired, as shown by the sparseness of the leaves. 



The beetles were unusually frequent in Brunswick during late July 

 and especially in August, 1884, at this time laying their eggs. Al- 



FiG. 139. — Mine of Glycobius speciosus in bark alone. Natural size. 



though none were found engaged in the operation, there is little doubt, 

 as will be seen below, that the process is nearly identical with that of 

 the pine-borer, or Monohammus. I found two mines of this borer 

 which crossed each other (Fig. 138), though usually each follows an in- 

 dependent course, unless much crowded. On a single tree from one 

 side of which the bark had fallen off in consequence of the attacks of 



