FAMILY SCOLYTIDAE 555 



apparently prefers the older trees whose bark is thicker ; when attacking 

 poles, it confines its operations more especially to the lower three-quarters 

 of the bole, leaving the upper quarter and the branches to its companions, 

 Polygraphs major (p. 501) and Pityogcnes conifcrae (p. 562). 



The injuries to the tree are confined to the bast layer, and when it is 

 badly infested this part of the tree is completely riddled and destroyed, 

 resulting in death. Attacked trees can be recognized by the shot-hole 

 borings in the bark, each having a little sawdust at its entrance which has 

 been ejected by the beetles when making the burrow. If trees with 

 large numbers of these holes on their outer bark be cut into, the 

 cambium layer will be found to be swarming with either larvae, pupae, or 

 beetles. 



Sickly trees, ringed trees, and newly felled ones are at once attacked by 

 it, and its powers of rapid multiplication which have been shown to be very 

 great, owing to the number of eggs laid by the beetle and the number of 

 generations it is capable of passing through during the year enable it to 

 spread rapidly over large areas. When particularly abundant in a locality 

 I have found it attacking green healthy trees. It does not attack barked 

 trees, and it has not been found in stools or stumps. 



Ringing trees to allow them slowly to die is a sure method of increasing 

 the numbers of this insect in a forest, since the beetles will resort to these 

 trees, which are in the exact condition they prefer for egg-laying. Also 

 heavy fellings, when the bark is left on the trees from two to three months 

 after the trees have been felled, are favourable to an increase in the numbers 

 of this beetle. Wind- and snow-breaks are similarly taken advantage of if 

 left unbarked in the forest. 



The Tonricus insect must be looked upon as all the more dangerous 

 owing to the fact that it attacks equally the blue pine and spruce. 



The probable working in the near future of areas containing these 

 species on a far larger scale than has been the case makes it imperative 

 that a first-hand knowledge of this beetle's life history and capabilities for 

 damage in the forest should be possessed by the Forest Officer in charge of 

 such work. 



These are very similar to those given in detail lor the deodar bark- 

 borer on p. 572. Stress must be laid, however, on the 

 Protection and r i t i> r 11 



Remedies great usefulness of trap trees. l>y felling a few ot 



these at intervals through the year (middle of April to 



end of November), and keeping them under supervision, it is quite possible 

 for the Range Officer to keep himself fully acquainted with the abundance of 

 bark beetles in his forests, and in the event of the insects suddenly beginning 

 to increase in unusual numbers it will place; him in a position to give early 

 intimation and warning of this fact to his Divisional ( Mticer. 



The girdling of blue pine and spruce to encourage the regeneration of 

 deodar, if carried out, should be done in such a manner thai the girdled trees 



