50 Forests and Trees 



of that is limited in any natural forest, they are not plentiful 

 enough to be a serious pest. Only occasionally do they 

 attack living trees. Lumbermen and others, in cutting 

 timber and leaving the refuse on the ground, have provided 

 breeding places in unusual quantities. This has caused 

 the insects to increase to such an extent that they have 

 swarmed out of the dead bark and attacked living trees 

 in very large numbers. Some idea of the numbers of the 

 insects and the seriousness of the recent attack may be 

 gathered from the fact that the entomologist who in- 

 vestigated conditions in one locality reported that "from 

 1500 to 2000 pairs of beetles were cutting tunnels and de- 

 positing eggs in the lower fifty feet of many of the infested 

 trunks examined." 



The destruction so far has not been on a scale sufficient 

 to affect any large percentage of the immense forests of 

 British Columbia, but every infected tree or group of trees 

 forms a centre from which the surrounding timber becomes 

 subject to attack. Trees in the vicinity of towns or where 

 lumbering has been done are in special danger. 



Other insects in myriads are constantly attacking forest 

 trees. The green aphis has been a serious pest on the Mani- 

 toba maples in Manitoba and Saskatchewan, caused no 

 doubt by an abnormal increase in the number of trees since 

 the region has been settled. A natural check will no doubt 

 prevent wholesale destruction, but much damage has been 

 done* in places. A small yellowish beetle, the western 

 willow-leaf beetle, has done considerable harm some seasons 

 to the willows and poplars in the prairie provinces, and 



