ENEMIES OF CONIFEROUS TREES 265 



of their powerful jaws. We have known not only 

 the Scotch Pine and Spruce to be attacked by this 

 formidable insect, but quite a number of larch 

 planks were forwarded to us from northern England 

 that were rendered worthless as timber owing to 

 the attacks of the Giant Sirex. Prevention is 

 better than cure in dealing with this insect, and 

 fallen and felled trees should be removed from 

 the woodlands as quickly as possible. Weakly 

 or damaged trees and old stumps should also be 

 dealt with. The Tree Wasp is common on the 

 outskirts of London, and its boring may be seen 

 on some of the old and diseased Scotch Pines on 

 Hampstead Heath. Owing to the borings or holes 

 being perfectly circular in section and the edges 

 sharply defined, they are readily distinguished 

 from those of any other timber - destroying 

 insect. 



Wood Wasps are by no means uncommon in 

 the British Isles, and have been found on the 

 Larch, Spruce, Silver Fir, and Cedars. They 

 are formidable and splendid insects — S. gigas 

 being black and yellow, like the common wasp, 

 while S. juvencus is of a shining steel-blue, with 

 reddish markings on the male. The larvae are 

 stout white grubs, which bore obliquely towards 

 the heart of the tree, and often the galleries are 

 in such numbers that the tree is killed thereby, 

 and the timber rendered useless in consequence. 

 I have found S. juvencus ver}^ plentiful on the 

 Scotch and Cluster Pine, in Kent. Where Wood 

 Wasps abound, dead and dying trees should be 

 removed before the imagos appear in summer. 



Spruce - gall Aphis {Chermes ahietis) . — The 



