142 



THE SCOLYTID BEETLES. 



ECONOMIC FEATURES. 



It is said that this species prefers to attack the bark on the base of 

 the trunks and roots of sound or healthy trees, and that the connect- 

 ing of the broad larval chambers from the same egg gallery or from 

 several galleries has the effect of girdling the tree, either causing its 

 death or a weakened condition which attracts other barkbeetles to 

 complete the destruction. Young as well as old trees are attacked, 

 but, while this species will breed in standing injured or weakened 

 trees, it rarely breeds in felled ones. It apparently prefers the 



spruces, but will, according to dif- 

 ferent authors, attack pine, fir, 

 and larch. 



The evidences of attack are 

 masses of gum or resin and so- 

 called pitch tubes, mixed with 

 reddish boring dust. 



METHODS OF CONTROL. 



Removing the bark from the in- 

 fested trunk and roots, or scorch- 

 ing it if not removed, is recom- 

 mended to kill the broods. Coat- 

 ing the trunks of the trees with 

 a preparation of tobacco water, 

 Spanish blood, lime, fresh cow 

 dung, etc., is recommended as a 

 preventive. 



After the above was written 

 the writer received a paper on the 

 genus Dendroctonus from Dr. G. 

 Severin (1908), director of the 

 Royal Museum of Natural History 

 of Belgium. A large series of 

 specimens of the beetle and its 

 work was also received from Doctor Severin, which was of special 

 value and interest. Doctor Severin' s paper covers the more impor- 

 tant historic and economic information on the species recorded in 

 European literature to 1908. Some of the information in the paper 

 that is of special interest in connection with a discussion of all of 

 the species is summarized as follows: 



Information from Paper on the Genus Dendroctonus, by Dr. G. Severin 



(1908, pp. 1-20). 



Dendroctonus micans alone, of all the hylesinids, and perhaps of all the scolytids, 

 appears to love the resin and to live there with ease. It neglects the weak trees and 

 is found principally upon trees full of vigor, of an age of 30 years and more, where it 



Fi3. 92.— The European spruce beetle {Den- 

 droctonus micans): Adult. Greatly enlarged. 

 ( Author's illustration.) 



