112 THE SCOLYTID BEETLES. 



living parent adults or developing broods, efforts should be made 

 toward its control. The individual trees and groups of trees attacked 

 during the spring and summer should be located and marked during 

 August and November. In order to effectively check its ravages, at 

 least 75 per cent of the infested trees should have the infested bark 

 removed from the main trunks or the logs converted into lumber 

 and the slabs burned during the period beginning with the first of 

 November and ending with the first of the following March. 



The simple removal of the bark during this period, without burning 

 it, will be sufficient to kill the broods. The bark may be removed 

 from the trees as they stand or after they are felled, as may in each 

 case be most convenient or desirable. 



The operations should be confined first to the worst infested locali- 

 ties and to the larger clumps of infested trees. Therefore explora- 

 tions should be made from time to time to determine the principal 

 localities in which the ravages of the insect are sufficiently extensive 

 to require special attention. 



If it is more convenient or practicable to fell the trees and roll the 

 infested trunks together and burn them, the work should be done 

 during the winter months. 



With this species the barking of newly infested trees during July 

 and the first half of August is permissible and sometimes desirable, 

 because this is the period in which the principal larval development 

 takes place and before the broods of adults have sufficiently matured 

 to fly when liberated from the bark. By the last of August some of 

 the adults have developed sufficiently to fly; therefore the infested 

 trees should not be barked during the latter part of August and through 

 September and October. 



The fact that this species is attracted to the living bark on the 

 trunks and stumps of recently felled trees suggests the efficiency of 

 the trap-tree method of control. Whenever it is found desirable to 

 adopt this method living trees should be felled in August and 

 April and have the bark removed or the logs utilized and the slabs 

 burned to kill the broods, the former during the winter months and 

 the latter during the following July and the first half of August. 

 Experiments with girdled trap trees show that girdling is by no means 

 as effective as felling. 



Continued timber-cutting operations within a given locality, espe- 

 cially in the coast region, usually serve to protect the living timber 

 from attack by this beetle, because the stumps, logs, tops, and broken 

 or injured Douglas fir trees furnish all the requirements for its 

 breeding, and the utilization of infested logs destroys large num- 

 bers of the beetles. If, however, the living timber in the vicinity 

 of cuttings should at any time become threatened by an invasion 

 from the cuttings, or if it be desirable to include in timber-cutting 



