FAMILY SCOLYTIDAE 



469 



danger of green trees being attacked in the forest is entirely dependent on 

 two factors : 



1 i ) The presence in the forest of a sufficiency of felled trees, windfalls, 



and standing sickly trees. 



(2) The abundance of the insects in the locality. 



In the first case the presence of such trees leads to the increase of the 

 beetles, since the 

 conditions favour 

 them. In the second 

 case it should be pos- 

 sible to reduce to a 

 minimum the dan- 

 ger of serious infes- 

 tations of the insects 

 by removing or bark- 

 ing at once all felled 

 trees and windfalls, 

 and removing al 1 

 standing sickly trees, 

 which, if left, serve 

 as centres in which 

 the insects raise a 

 numerous progeny. 



Coniferous trees 

 infested by bark- 

 boring Scoly tidae are 

 easily distinguish- 

 able when standing 

 in the forest : 



( i ) The foliage 

 turns yellow and the 

 needles commence 

 to drop off. 



u) The b;i rk 

 shows on the out- 

 side numerous pin 

 or shot holes, made 



by the beetles en- | . M; 3 , . Kxit-holc-s, or "shot-holes," of mature .Vy 



tering the tree or \/uvr//7YA7.v hectics on outer surface of the lurk of a s.il tre . 



issuing from it. 



(3) The bark shows on tin- outside under the entrance- holes made by 

 the beetles elongate pear-shaped drops or 'tears" <>l resin. Trees so 

 affected are said to "weep," and in tin- case of seriously infested trees the 

 tears, often forming a drip down the kirk for some distance, are very easily 

 seen and are characteristic of the attack. I'l. \li shows the bark of 



mam 



