THEIR RELATION TO PLANTS 71 



living or dead. The name bark beetle is a misnomer 

 for many of the species, which never bore into or 

 under bark at all; but it applies well to a very large 

 number that make characteristic borings or galleries 

 beneath the bark or in the sap-wood. In forms of 

 which the common fruit bark beetle may be considered 

 typical, the adult bores a longitudinal channel in the 

 sap-wood and lays eggs on each side in little notches 

 cut for that purpose. These beetles are all more or 

 less cylindrical, slender and elongate, with a very short 

 or scarcely perceptible snout and well-developed jaws 

 or mandibles. The larvae that hatch from the large 

 white eggs are of the usual grub-shape, white with 

 brownish head, and each larva makes its burrow at 

 right angles to the main gallery, diverging a little up- 

 ward or downward as it increases in size so as to avoid 

 its neighbors, and making a pattern so distinctive 

 that the species may be recognized by its borings alone. 

 Quite usually beetles of this character attack trees that 

 are a little weakened or unhealthy, but some take to 

 perfectly sound trees and cause serious trouble. Other 

 species bore into the heart wood, their galleries being 

 cylindrical, often blackened or discolored, and these 

 are sometimes called shot-hole borers. 



No kind of tree is exempt from the attacks of 

 such beetles, and thousands of acres of forest lands 

 in all sections of the United States are annually de- 

 stroyed by them. And much timber is rendered useless 

 or lessened in value by the borings which disfigure or 

 weaken it, where the life of the tree itself is not threat- 

 ened. In trunk, in twig and even in the roots these 

 Scolytid borers are found, and our knowledge of them 

 still leaves much to be desired. Only a small propor- 

 tion of our species are actually known, and their classi- 

 fication at present is merely tentative. They are re- 



