THE WESTERN PINE-DPJSTROYING BARKBEETLE. 27 



is made larger to accommodate the size of the body. Having readied 

 the outer bark, it hollows out an oval space or pupa case, in which to 

 go through its transformations. 



NATURAL ENEMIES. 



Larvae of the predaceous beetles of the genus Clerus, which are 

 known to prey upon Dendroctonus larva?, were quite common in and 

 under the bark of the infested trees, and they doubtless help to some 

 extent in keeping down the numbers of the barkbeetles. 



Birds contribute their part also in destroying larvae and pupae. The 

 work of woodpeckers was found upon most of the trees which had 

 been killed by D. brevicomis, and these birds had evidently destroyed 

 a large percentage ol the insects in some of the trees. 



METHODS OF COMBATING THE INSECT. 



FIRST RECOMMENDATIONS. 



The following information and recommendations relating to this 

 insect and methods of preventing losses from its ravages were conveyed 

 by Doctor Hopkins to Mr. E. M. Hoover, or Boise, Idaho, manager of 

 the Payette Lumber and Manufacturing Company, in a letter dated 

 January 23, 1906, and afterwards published, with Mr. Hoover's reply, in 

 a local newspaper. 



Our special field agent, Mr. J. L. Webb, has submitted his report on forest insect invest i- 



i gations in the vicinity of Centerville and Smiths Ferry, Idaho, during the past summer, and 



it will interest you no doubt to know that the insect which is primarily to blame for the death 



!of pine trees was located and thoroughly studied by him. 

 He found that the broods of the destructive species pass the winter in the grub state in the 

 bark of trees which died during the late summer and fall and that they do not transform to 

 the v inged form and emerge until after the 1st of May. Therefore the method of combating 

 the pest is simply to cut the infested trees any time between the 1st ol October and the 1st of 

 May and to remove the bark from the main trunk and burn it. 



It is necessary to burn the bark in order to kill the broods of this insect, because they 

 occupy the intermediate portion between the inner surface and the outer scale portion: 

 hence the drying of the removed bark will not kill them as it would if they occupied the 

 inner moist portion. 



The infested trees can be located (1) by the yellowish and light reddish brown color of the 

 foliage; (2) by cutting into the bark as high up on the trunk as a man can reach with an ax 

 to determine whether the middle portion of the bark is infested with the small white grubs, 

 which are about three-sixteenths of an inch long. If these arc found, it will be conclusive 

 evidence that the tree has been killed by the beetle and is infested with its broods. It must 

 be remembered that there are hundreds of other kinds of insects which occupy the inner por- 

 tion of the bark and wood of such trees, but none of the smaller ones pass the winter in the 

 <W terbark. * * * 



Perhaps the most important thing for you to do as a preliminary to any definite action you 

 may take in the mallei is to have a number of intelligent cruisers make a survey of your 

 holdings for the purpose of local ing the pi incipal sections m which trees have died during the 



