46 Forests and Trees 



locality, leaving its natural enemies behind. Freed from 

 the control of these, it multiplies enormously and does 

 great harm. Thus insect pests like fires follow in the 

 wake of man, and if he cannot by intelligence re-establish 

 the balance where it has been disturbed, then a general 

 and perhaps disastrous readjustment will have to take 

 place. Whole forests may be destroyed before the food 

 of a particular insect is sufficiently reduced to check its 

 increase, or the growing of a valuable food crop may have 

 to be abandoned. 



Some very notable examples of destruction of forest 

 trees by insects have occurred in Canada in recent years. 

 The one which has become best known is the destruction 

 of the tamaracks in Ontario and Quebec by the larch 

 sawfly. This insect, in the larva form, eats the leaves off 

 the eastern larch or tamarack, and repeated defoliation 

 soon kills the trees. As this tree usually occurs in swamps, 

 where it constitutes a very large percentage of the growth, 

 the opportunity for the increase of the pest was particularly 

 good. Nature had planted forests of a single species and 

 the inevitable result happened. The destruction, which 

 began several years ago, is almost complete in the two 

 large central provinces, and the pest has followed the 

 tamarack westward into Manitoba. Not only this fine tree, 

 but also the two kindred species of larch in British Columbia 

 are threatened with destruction. Yet this same insect 

 has existed in Europe for some centuries and has not de- 

 stroyed the larch. Serious outbreaks occur in places at 

 times, but these are checked by natural control before 



