564 



Canadian Forestry Journal, June, ]iji6. 



in the United States. Wo. have not 

 yet sufficient information to enable 

 us to make any definite estimate of 

 its value, but it certainly amounts to 

 many millions of dollars annually, 

 probably varying between twenty- 

 five and seventy-five millions. 



The most important insect en- 

 emies of Canadian forests may be 

 considered under the following 

 heads : Borers in trunks of living 

 trees ; Borers in logs and trunks of 

 standing dead trees : Defoliating in- 

 sects ; Bark-beetles in livino- trees, 

 and Borers infesting wood products. 

 A few representatives of each group 

 will be mentioned. 



Borers in Liz'ing Trees. 



The well-known Poplar Borer, 

 Saperda Calcarata, is an excellent ex- 

 ample of this group. Everywhere 

 abundant, its large whitish grubs 

 perforate the trunks of poplars with 

 large irregular tunnels, thus weak- 

 ening the trunk, checking the 

 growth and admitting fungus spores 

 to aid in the more rapid destruction 

 of the tree. In some districts full- 

 grown poplars are almost unknown. 

 There is no method of control ap- 

 plicable under forest conditions. 



The Locust Borer, Cyllenc robi- 

 niae, is practicaly exterminating the 

 locust trees in parts of Ontario. A 

 block of these trees in the forest belt 

 about the Central Experimental 

 Farm at Ottaw^a is now practically 

 destroyed by them. 



The Western Cedar Borer, Tra- 

 chekele sp., an enemy of British Co- 

 lumbia cedar, is the most important 

 of our borers in living trees, wdien 

 the value of the timber destroved is 

 considered. Although a closelv re- 

 lated beetle has long been known in 

 Washington and Oregon forests, 

 this injury has only recently been 

 reported from British Columbia. 

 That it has been working there for 

 many years we know. The grubs 

 are found working only in living 

 trees, and this summer Mr. Chrystal 

 and I found its old tunnels in cedar 

 logs, which had been killed by fire 



eighteen years ago. The grubs cut 

 flat slightly winding, longitudinal 

 tunnels through the heart wood or 

 more rarely in the sap wood of the 

 middle three-fourths or four-fifths 

 of the trunk, usually working up- 

 wards end ending their tunnels in a 

 pupal cell in the branches; a single 

 tunnel was traced for forty feet. The 

 tunnels seldom extend to the but 

 end or to the extreme top and do 

 not show at all upon the wood sur- 

 face when the bark is removed, so 

 that when the tree is felled and trim- 

 med there is usually no evidence of 

 any trouble, although the heart 

 wood may be very thoroughly rid- 

 dled with tunnels. Even when the 

 timber is cut into logs or shingle 

 bolts the injury is easily overlooked, 

 for the tunnels are flat and filled 

 with boring dust of the same color 

 as the surrounding heart wood. We 

 have never found the larvae in dead 

 trees and only seldom in perfectly 

 healthy trees ; usually they occur in 

 "dead-top" cedars. The habits of 

 the beetles and the distribution of 

 the injury in British Columbia are 

 being carefully studied this summer. 

 These three examples will illus- 

 trate the type of injury caused by 

 borers in living trees. Other injuri- 

 ous insects with somewhat similar 

 habits infest both eastern and west- 

 ern forests. 



Ruin of Valuable Logs. 



Pine and spruce logs and standing 

 trees, killed by fire or bark-beetles, 

 are usually very badly riddled or 

 destroyed for commercial purposes 

 if left unprotected in the woods for 

 two season, or even for one. The 

 chief injury is caused by large whit- 

 ish legless grubs, the young of large 

 long-horned laeetles belonging chief- 

 ly to the genus Monohaninius. The 

 grubs work in the wood for two sea- 

 sons, going deepest and causing the 

 most injury during the second sea- 

 son. An account of an example I 

 saw last summer will illustrate very 

 well this type of injury. On the 

 north shore of Lesser Slave Lake 



