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.) 
