48 
THE SCOLYTID BEETLES. 
It has been determined that this species can be attracted to girdled 
and felled trap trees. Under certain conditions, therefore — as in the 
case of the absence of logging operations and where only a few scat- 
tering trees are infested — it may be desirable, as a means of main- 
taining control, to provide a few trap trees to attract the first genera- 
tion. This can be done by girdling two or three inferior trees to 
the heartwood or by felling them in June. Then, if they become 
infested with this beetle, the bark should be removed from the main 
trunk and burned by the middle of August. Trap trees to attract 
the second generation should be prepared in August and September 
and barked before the first of the following May. Usually an aver- 
age of one to three trees to the acre should be sufficient for this 
purpose. However, the number will depend largely upon the preva- 
lence of the insect. (See preceding reference to trap trees, pp. 33-34.) 
Fig. 11.— The western pine beetle: Distribution map. (Author's illustration.) 
Continued timber-cutting operations within an area of from 20 
to 50 square miles usually provide sufficient breeding places in the 
bark of the logs and tops of the felled trees to satisfy the requirements 
of this species; but if the living timber should be at any time threat- 
ened by the broods emerging from the slash, or if it is desirable to 
include in timber-sale and timber-cutting regulations certain provi- 
sions for the burning of the slash, this work should be done about the 
first of August for the slash of the winter and spring cutting, and dur- 
ing the winter for that of the late summer and fall cutting: the latter 
period, however, is preferable, on account of the danger of starting 
forest fires bv summer burnins:. 
