40 THE SCOLYTTD BEETLES. 



July will usually have the foliage Fading Off turning yellow in August; 

 those attacked in August may have the foliage fading in vSeptember 

 and October, while those attacked in September may fade during 

 the late fall or winter or remain green until the following spring. 

 All, however, will have yellow to reddish foliage before the broods 

 have entirely emergen] the following July. As a rule, all of the broods 

 will have emerged from the trees found at any season with reddish 

 to brown and falling foliage. The exceptions are when only part of 

 a- tree or the bark on one side of the trunk is killed by the first attack, 

 and the remaining living bark is infested later in the same season or 

 during the next. Positive evidence that the above conditions are 

 caused by this species must be based on authentic identification of 

 specimens found in the bark of trees so affected, 



EFFECTS ON COMMERCIAL VALUE OF THE WOOD. 



The commercial value of the wood of trees killed by this beetle 

 is reduced by the bluing of the sapwood, often before the leaves begin 

 to turn yellow, but the heartwood, especially of the larger trees, 

 does not deteriorate until decay sets in several years after the tree's 

 death. The loss, therefore, is not necessarily very great where the 

 timber is felled and utilized immediately after a destructive attack, 

 but if the insect-killed trees are left standing until the branches 

 and tops break off and fall (fig. 10), the loss is often serious or 

 complete. Serious losses of a secondary nature, both of the dead 

 and adjoining living timber, may often result from forest fires 

 started in the dead timber. Therefore the losses, first from the 

 ravages of this species and second by fire, have been severe in some 

 localities. 



FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. 



Favorable conditions for the multiplication and destructive work 

 of this beetle are found in areas of large, matured timber, and espe- 

 cially where such trees are frequently struck by lightning or injured 

 or felled by storms, etc. The unfavorable conditions for attack upon 

 the living timber are found in areas of vigorous, recently matured, or 

 young growth, and where timber-cutting operations are continued 

 from year to year under modern systems of forest management. 



METHODS OF CONTROL. 



In localities and areas of greater or less extent where it is known 

 that scattering clumps of trees are dying from the attack of this 

 species, the principal clumps of infested trees should be located in 

 September to March, and the infested bark on the main trunk and 

 larger branches removed and burned, or the logs converted into lum- 

 ber and the slabs burned. This work should be begun not earlier 



