FA M I L Y S C O L ^ r 1 1 ) A E 



469 



(laiif^er of ;;reen trees beinj; attacked in the forest is entirely dependent on 

 two factors : 



(1) The presence in the forest of a snfficiency of felled trees, windfalls, 



and standin^^ sickly trees. 



(2) The abnndance 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. Inthesecond 

 case it should be pos- 

 sible to reduce to a 

 minimum the dan- 

 ger of serious infes- 

 tations of the insects 

 b}- removing or bark- 

 ing at once all felled 

 trees and windfalls, 

 a n d re m o \' i n g all 

 standing sickly trees, 

 which, if left, serve 

 as centres in which 

 the insects raise a 

 numerous progen}-. 



Coniferous trees 

 infested b\' bark- 

 boringScol}'tidaeare 

 easily distinguish- 

 able when standing 

 in the forest : 



(1) The foliage 

 turns \ellow and the 

 needles commence 

 to drop off. 



(2) The bark 

 shows on the out- 

 side numerous pin 

 or shot holes, made 

 b\^ the beetles en- 

 tering the tree or 

 issuing from it. 



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

 the beetles elongate pear-shaped drops or "tears" of resin. Trees so 

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

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

 seen and are characteristic of the attack. PI. xli shows the bark of 



Fig. 310. — Exit-holes, or '' shot-holes, " of mature Sphaerotrypes 

 siwalikensis beetles on outer surface of the l:)ark of a s;il-tree. 



