16 



The over-wintered larvae complete their transformations, emerge from the 

 bark as adults, from the middle of July onwards, and start their egg-tunnels, 

 probably at once, in the trees already infested. 



At Princeton, this season, practically all the broods had emerged from the 

 red-tops examined (trees attacked the previous summer) by the latter part of 

 August. 



The exact time of emergence of the different over-wintered broods will 

 depend to some extent upon the altitude, location of the trees in regard to 

 sunlight, and upon the lateness of the season. 



SUMMARY OF SEASONAL HISTORY. 



Over-wintering Forms. Parent adults; young adults; larvae of the second 



brood. 

 Seasonal History of Over-wintered 



Parent Adults. Eggs, April and May; adults appear during August. 

 Young Adults. Attack timber, and eggs laid early in July; larvae 

 maturing and adults emerging from late August onwards; egg- 

 tunnels cut and eggs laid for a second brood, which winters as 

 larvae in the middle layers of bark. 



Over-wintered larvce. Transform to pupae in late April and May, accord- 

 ing to season, and emerge from the trees as adults daring July 

 and August. 



PRACTICAL ASPECTS OF THE LIFE-HISTORY. 



This species over-winters in the middle layers of the bark of the recently- 

 infested trees, those with yellowing foliage. The adults appear in large numbers 

 from June onwards, and spread the infestation to green timber. When green 

 trees are attacked, the exuding resin forms in gum-tubes about the mouths of 

 the entrance-holes, and the presence of these gum-tubes upon the bark serves 

 to distinguish the infested trees before the foliage has faded. The foliage of 

 the infested trees begins to fade from the middle of August onwards, turning 

 yellow during the winter and early spring and becoming red by early summer. 

 The trees with red foliage are known as " red-tops." The treatment of the red- 

 tops is useless in control measures against the Bark-beetles; for, by the time the 

 foliage is red, the beetles have already escaped, or are rapidly emerging, and 

 they invariably enter logs or timber recently infested, dying, or green and 

 sound, never trees with red and, therefore, dead foliage. 



CONTROL MEASURES FOR THE WESTERN PINE BARK-BEETLE. 



Outbreaks of this and other injurious Bark-beetles in British Columbia 

 if taken in time, can be controlled by logging operations modified so as to include 

 the trees containing the brood, and employing proper means for destroying the 

 latter. The beetles and grubs pass the winter in the bark of the trunk of trees 

 attacked that season, on which the foliage is still pale-green or yellow, with the 

 bark studded with gum-tubes. If over three-fourths of the infested trees can 

 be handled so as to kill the contained brood before they emerge in the early 

 season, the outbreak can be checked; and by similar work upon the relatively 

 few trees attacked the succeeding season, can be brought under nearly complete 

 control. 



When it becomes necessary to undertake direct control measures, the 

 broods in the bark of the infested trees can be destroyed by whichever of the 

 following methods are best suited to local conditions: 



