30 . THE SCOLYTID BEETLES. 
while others, as in subdivisions B, C, and D, transform in the 
inner bark: (<?■) the broods of all of the species pass the winter in 
the bark of the infested trees and remain there until they develop 
to the winged stage, when they leave the then dying or dead trees 
to fly and attack the living ones; (<?) the developed broods of beetles 
usually emerge from the trees before the leaves are all dead, or cer- 
tainly by the time the leaves have all changed to the reddish-brown 
color and begin to fall or have entirely fallen from the branches. 
(See fig. 25.) 
DESTRUCTION OF THE BROODS. 
Since the trunk of the tree is the principal part of attack, we have 
only to direct our efforts to the infested bark on the main trunk, and 
adopt the method of killing the broods which, under local conditions 
and facilities, is the most practicable and efficient. 
In species 1 to 8 removing the infested bark, and burning or 
otherwise destroying it, is necessary to kill the developed broods of 
larvse, pupa?, and adults which may be located in the outer bark. 
In species 9 to 23 the removal of the infested bark without burn- 
ing is all that is necessary. The time to do the work in both cases 
is from the time activity ceases in the fall until two or three weeks 
before the normal time for the winged adults to begin to emerge 
and fly. 
BARKING THE STANDING TREES TO KILL THE BROODS. 
The bark may be removed from the standing trees by means of 
suitable tools (see figs. 57, 58), and the trees left until it is convenient 
to fell and utilize them. Thus, during the period in which these 
operations must be done, the labor should be directed exclusively 
to the removal of bark. If necessary, the barked trees may be left 
standing for several years without the value of the wood becoming 
impaired; otherwise their utilization may immediately follow the 
completion of the barking operations. Whenever the conditions 
are favorable for the immediate disposal or utilization of the infested 
timber by sale, free use, or otherwise, the timber may be barked as 
it is felled and the barked log may be converted into lumber at any 
time during the year, within the required period. 
DESTRUCTION OF THE BROODS WITHOUT REMOVING THE BARK. 
The destruction of the broods without removing the bark may be 
accomplished by several different methods: (a) By converting the 
logs into lumber and burning the slabs: (b) by placing the logs in 
water; (c) by piling the trunks and scorching the bark sufficiently 
to kill the broods; (d) by scoring the upper side of the felled trunks 
to allow the water from rain or melting snow to penetrate the inner 
