150 PROTECTION OF WOODLANDS. 



74. Other Cambial Beetles, Hylesinini. 



Among these may be mentioned the following, on account of 

 their occasionally occurring as very injurious insects : 



The large Spruce cambial beetle, Hylesinus (Dendroctonus) 

 micans, characterised by its size, 0'32 to 0*36 inches, and also by the 

 fact of the larvae living and feeding in family or common galleries 

 under the bark as in the case of BostricJius laricis. They chiefly 

 attack standing timber, and frequently bore into Spruce trees 

 that are perfectly sound, for the outflow of resin seems to in- 

 convenience them much less than it does other species of bark 

 and cambial beetles. At the same time the beetle usually bores 

 into stems and poles immediately above the ground, where its 

 presence is betrayed by the resinous exudations. Protection and 

 prevention are difficult, being confined to the felling and barking 

 of stems that have been attacked. 



The black Pine Cambial Beetle, Hylesinus (Hylastes) ater, and the 

 black Spruce Cambial Beetle, Hylesinus (Hylastes) cunicularis, exhibit 

 many points of resemblance in their habits and life-history. 

 Both belong to the root-boring class, and, along with a number of 

 other less frequent cambial-beetles (Hyl. angustatus, attenuate, 

 &c.) deposit their ova somewhat early in spring within the fresh 

 stumps and roots of recently-felled conifers, the former princi- 

 pally on Pine stumps, the latter mostly on Spruce, where the 

 larvae soon begin to feed throughout the cambial layer, but 

 without forming any distinct sort of galleries, as the whole sub- 

 stance between the wood and the bark becomes transformed by 

 them into a brownish kind of bore-dust. But towards the end of 

 June the beetles make their appearance, and migrate to young Pine 

 and Spruce thickets, where they attack the tender bark near the 

 neck or upper part of the roots, and also gnaw it near the base of 

 the stem. In the latter case they also at the same time bore 

 under the bark, and often make tunnels in the cambium right round 

 the bole, so that plants only slightly injured sicken in growth 

 (wilt), whilst those badly injured soon die off. 



The grubbing up of stumps, and, as far as practicable, of all 

 the roots, especially during May and early in June, after ovi- 

 deposition has taken place, the burying of decoy-sticks in the 

 ground as breeding-places for the second generation, the pulling 

 out and burning of saplings or young transplants that are of 



