30 THE SCOLYTID BEETLES. 



while others, as in subdivisions B, C, and D, transform in the 

 inner bark; (d) 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 ; (e) 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 

 larvae, pupae, 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 BAEK. 



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; (5) by placing the logs in 

 water; (c) by pihng 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 



