THE BLACK HILLS BEETLE. 17 



numbers to materially aid their increase. Indeed, newly fire- 

 scorched trees observed near a sawmill in the Manitou Park section 

 showed no trace of the presence or work of this beetle, although the 

 trees were being attacked by several species of secondary enemies, 

 including the true turpentine beetle (Dendroctonus valens Lee). On 

 the other hand, an extensive forest fire may contribute to the destruc- 

 tion of the Black Hills beetle by burning the dead bark from the liv- 

 ing and dying infested trees, which may explain the evident sudden 

 endings of old invasions. 



COMMERCIAL CUTTING. 



The cutting of living trees for commercial purposes has appar- 

 ently little or no influence on the multiplication of the beetle. While 

 it will breed in freshly cut logs from living trees, our experiments 

 show that it prefers to attack standing timber. Then, again, any 

 operations which involve the removal of the bark from the logs for 

 ties, mining timbers, etc., will destroy any broods which may be 

 therein. If cut into cord wood, the bark will soon become too dry 

 for the insect to live in. Slabs from freshly cut logs may favor its 

 development in small numbers, but usually the conditions in such 

 material are not favorable. Neither do the green stumps, so far 

 as we have observed, offer sufficiently attractive breeding places 

 for this beetle to warrant the barking of such stumps. Nothing in the 

 slash will offer favorable breeding places, except the tops of the main 

 trunk, and this is seldom sufficient to warrant any special treatment. 



SUMMER CUTTING IN PATCHES. 



The cutting of living infested trees and of healthy trees in local 

 commercial cuttings is objectionable from the fact that we have 

 found that when a few living trees are felled in the midst of a forest 

 where this beetle is present in numbers it will be attracted by the 

 odor and will attack the surrounding standing timber. Therefore 

 such local summer cuttings should be avoided. 





TRAP TREES. 



This is a method of combating bark beetles in which trees are 

 girdled or felled to attract the insects to them, after which the broods 

 are destroyed by stripping off the bark or burning the entire tree. 



Trap-tree experiments were conducted by Mr. J. L. Webb, under 

 the writer's instructions, in the Black Hills Reserve in 1902, in which 

 trees were felled, hack girdled, girdled to the heart wood, belt girdled, 

 and hacked and peeled at intervals of five or six days between June 

 2 and October 30. The result of this experiment showed conclu- 

 sively that no method of preparing the trap trees was o( sufficient 



