THE GENUS DENDROCTONUS. 51 



continue to come out until September, or later. Mr. Webb's observa- 

 tions on the development of the broods from the time eggs were 

 deposited on June 4 and June 9 to the beginning of emergence on 

 July 22 and July 29, show a period from deposition of eggs to emer- 

 gence of adults of about fifty days. 



The principal period of flight of the adults of this generation appears 

 to be during the latter part of July and first of August, but it is evi- 

 dent that while some of the more retarded broods may hibernate as 

 matured adults and larvae, nearly all develop and emerge before 

 activity ceases in the fall. 



SECOND GENERATION. 



The records of observations indicate that the earlier emerged adults 

 of the first generation attack the trees and begin to deposit eggs 

 about the first of August, the principal attack being in August and 

 September. 



The larvae begin to hatch early in August and begin transforming 

 to pupae about the 1st of September, but no adults of this generation 

 have been observed during the first season. The winter is passed in 

 all stages of larvae, with some of the parent adults. Therefore, there 

 is one complete seasonal generation and a partial development of a 

 second, or two complete generations annually. The principal differ- 

 ences in the seasonal history and generations of species 1 and 2 are 

 the earlier beginning and ending of the first period of attack by the 

 overwintered broods of No. 2, and the more complete development 

 of the second generation. The habits of the two species are quite 

 similar, except that the present species is usually associated with 

 one or more others — Nos. 3, 5, 8, and 10. 



ECONOMIC FEATURES AND METHODS OF CONTROL. 



The economic features and methods of control relating to this species 

 are quite similar to those of the western pine beetle. In case it should 

 become isolated from the other species of Dendroctonus with which 

 it is usually associated and become independently destructive, and if 

 summer barking of the infested trees should be found desirable, the 

 work should begin (under average conditions) about the middle of 

 June and end at the middle of July, or just a month earlier than for 

 the western pine beetle. The same rule applies for trap-trees for the 

 first generation, which should be prepared in May and barked by the 

 middle of July. The fall and winter work of barking trees may begin 

 a little later, but should be completed by the 1st of May. In the 

 more southern range of this barkbeetle the beginning and completion 

 of such control work should be two months earlier than at the same 

 altitude in its more northern range. (See "Methods of control" 

 under western pine beetle, pp. 46-48.) 



