48 Forests and Trees 



the damage is very great. This is a case where man has 

 introduced a destructive insect into new surroundings 

 without also introducing its enemies. The larch sawfly 

 was brought from Europe no one knows how and 

 found here, in the swamps of almost pure tamarack, an 

 ideal place for increase of numbers. Having no natural 

 enemies to hold it in check, there was no limit to its in- 

 crease so long as the food supply lasted. Dr. C. Gordon 

 Hewitt, Dominion Entomologist, in speaking on this point 

 says: "The enormous havoc wrought by this insect was 

 apparently due to the fact that there existed no natural 

 means powerful enough to control it before it had destroyed 

 its food plant." This was because the insect was in new 

 surroundings. Where it had lived for a long period, it 

 must have been controlled, or it would have brought about 

 its own destruction by consumption of its own food. Man 

 must re-establish the natural check, or the tamaracks of 

 the continent are doomed. 



Another example of devastation on a large scale is found 

 in the injury done by bark beetles in the conifer forests of 

 British Columbia. The yellow pine of the southern in- 

 terior of the province is particularly liable to attack and 

 has suffered most, but the white pines and Sitka spruce 

 are also affected. There are several species of these beetles, 

 each working in its own way and attacking a particular 

 kind of tree, or in some cases a single species attacking 

 several kinds. The life histories, as well as the injuries 

 caused by them, are so similar in all cases that no dis- 

 tinction need be made here. 



