THE GENUS DENDROCTONUS. 105 



much overlapping of the overwintered and new broods during the 

 summer. The broods of the first generation begin to transform to 

 adults toward the last of July, at which time all stages from parent 

 adults to freshly transformed ones have been found. 



ECONOMIC FEATURES. 



Sufficient observations have been made to indicate that under 

 favorable conditions this may be a very destructive species. Like 

 most of its relatives, it attacks the largest and best trees, and when 

 aided by defoliating insects, like the larch worm, or by other bark- 

 beetles and bark-borers, it could easily devastate large forests. It 

 is evident, however, that its preference for the bark on the stumps 

 and logs of felled trees and those injured and dying from other 

 causes renders it much less dangerous than most of the other species, 

 and also much easier of control when it does attack the living timber. 



Favorable conditions for its destructive work will be found in large 

 forests of old matured larch undisturbed by the lumberman, where 

 many trees have been defoliated by the larch worm or injured by 

 fire, storms, etc., while unfavorable conditions for its work on the 

 living timber will be found in sections where continued timber-cutting 

 operations are carried on under a system of management requiring 

 the utilization of the older living larch timber, as well as any that is 

 dying or found to be infested with the beetle, as also when proper 

 care is taken of the young timber to facilitate a vigorous healthy 

 growth. 



METHODS OF CONTROL. 



Whenever it is positively determined that the larch is seriously 

 injured or dying from the ravages of this species, the infested trees 

 should either be barked, burned, or placed in water, and the stumps 

 barked, during the period between September and the following May. 

 Trap trees felled during May and June should serve to attract the 

 beetles away from living trees and thus facilitate their destruction 

 by removing the bark during the following fall and winter. 



BASIS OF INFORMATION. 



Information regarding this barkbeetle is based on investigations 

 by the writer in northeastern West Virginia and northwestern Mary- 

 land, near Cranesville, W. Va., May, 1897, in northeastern Maine, 

 June, 1900, and in northwestern Michigan, July and August, 1907, 

 and by Mr. W. F. Fiske in northwestern Michigan, October, 1906. 

 It is represented by more than 150 specimens in the West Virginia 

 Agricultural Experiment Station collection and by 180 specimens in 

 the forest-insect collection of the Bureau of Entomology. 



