566 



Canadian Forestry Journal, June, ipi6. 



tunnels from eight to fourteen 

 inches into the trunks, and occurs 

 in countless numbers in logs of 

 Douglas fir, western hemlock, low- 

 land balsm and Sitka spruce. It at- 

 tacks only weakened or dying trees 

 and logs. 



Defoliating Insects. 

 Among the best known of our for- 

 est insects are the defoliating or 

 leaf-eating species; of these the 

 larch saw-fiy, the spruce bud-worm, 

 and the tent caterpillars must be fa- 

 miliar to all, and illustrate the na- 

 ture of, the injury caused by insects 

 of this sort. A few of these defoliat- 

 ing insects are very seriously de- 

 structive in our forests, and unfor- 

 tunately we have no direct means of 

 combating them on large areas. Na- 

 ture controls them, in a longer or 

 shorter time, by means of their para- 

 sitic enemies and weather condi- 

 tions. We hope some day to be able 

 to assist materially in this control, 

 by the distribution of the parasites, 

 smaller insects which prey upon the 

 pests ; and the Entomological Branch 

 is studying these problems from that 

 standpoint. 



The Larch Sawfey, the most de- 

 structive of the group, has killed 

 immense quantities of larch within 

 the last generation, from Nova 

 Scotia as far west as Northern Sas- 

 katchewan, and will evidently ex- 

 tend its ravages throughout the 

 range of the eastern larch. The 

 larvae feed upon the leaves, and 

 when numerous entirely defoliate 

 the trees, and eventually kill them. 

 It does not yet occur on the western 

 larch in British Columbia, although 

 it feeds readily enough upon culti- 

 vated specimens of the western 

 species in the Arboretum at Ottawa. 

 The wide gap (nearly 600 miles) be- 

 tween the ranges of the eastern and 

 western larches will be a safeguard 

 to the latter species. 



The Spruce Bud-worm, in its cat- 

 erpillar stage, attacks the buds and 

 later the leaves of spruce, balsam, 

 Douglas fir, hemlock and larch. It 

 is most noticed in spruce ferests. 



While it has been known to kill 

 large numbers of trees, particularly 

 balsam, its parasites usually effect 

 control before very serious damage 

 is done. This has been the history 

 of the recent outbreak in the Quebec 

 and Ontario woods. It is always to 

 be feared that spruce weakened by 

 the bud-worm will be attacked by 

 destructive bark-beetles. For this 

 reason, bud-worm weakened spruce 

 should be watched during the sea- 

 sons following a bud-worm attack, 

 and if any considerable numbers of 

 spruce are found dying in clumps or 

 groups an investigation should be 

 made at once. 



Fire is, of course, our most serious 

 enemy to forest reproduction. Squir- 

 rels eat each season countless num- 

 bers of seeds, and immense numbers 

 of young trees are girdled and killed 

 by rabbits and porcupines. A large 

 amount of young black pine was 

 killed in this way, apparently by 

 rabbits, in the Jasper Park region 

 during the winter of 1914-1915. In 

 addition to these and other enemies, 

 reproduction is seriously affected in 

 many rgeions by injurious insects. 

 Certain species of caterpillars, beet- 

 les and chalcids feed within the 

 cones or seeds of pines, spruces, 

 hemlock, balsams, larch and Doug- 

 las fir, and more or less completely 

 destroy the seeds. Still other species 

 feed upon the seeds of certain de- 

 ciduous trees. The extent of this 

 seed destruction sometimes assumes 

 serious proportions, and its efifect 

 upon reproduction must at times be 

 most important. Certain species of 

 boring caterpillars are particularly 

 injurious to young growth of pines 

 by girdling and killing the branches 

 and tops an ddestroying or killing 

 the trees. The white pine weevil, 

 Pissodes strobi, is a serious enemy to 

 white pine reproduction in the east. 

 The grubs of this species destroy 

 the top or leader of young trees ; the 

 result is a "double-top" or at least a 

 distorted trunk of little use for lum- 

 ber. 



(To be continued in July issue.) 



