'27i TRANSACTIONS OF ROYAL SCOTTISH ARBOKICULTURAL SOCIETY. 



XXI. A Battle ivith Beetles. By John Clark, Forester, 

 Hacldo, Aberdeen. 



The Pine Beetle {Hylesinus 1 piniperda) is found more or less 

 in all Scotch fir woods. When the woods are in a healthy 

 condition they will be few, but if otherwise, they will be move 

 numerous ; and after a fall by a gale of wind, every twig of one 

 year's growth — in the neighbourhood of the fall — may be bored 

 and killed. 



After the gale of November 1893, the Pine Beetles increased 

 with alarming rapidity; and the gale of December 1894 supplied 

 them with a very large number of trees in condition for breeding 

 purposes, the result being that by the beginning of October 

 1896, almost every terminal shoot not under f^ths of an inch in 

 diameter contained one or more beetles. The consequence was 

 that thousands of the most vigorous Scotch fir trees died from 

 the attack ; and had it not been that many of the trees were 

 well matured, and that the main crop of their terminal shoots, 

 being under T ^-ths of an inch in diameter, were safe from 

 attack, not a single fir tree would have been left alive in the 

 woods that had been partly blown down by the gales. When 

 the blown-down trees were all dead, and were therefore of no 

 use to the beetles for breeding purposes, a large number of 

 standing trees that had the bulk of their annual shoots destroyed 

 by boring, became very weak, and offered the beetles the very 

 conditions they delight in for breeding purposes. In order to 

 save such trees, I prepared " trap " trees on a large scale, and by 

 the middle of March 1898 all the Scotch fir woods were provided 

 with them. The trees I selected for traps in which Hylesinus 

 piniperda might breed, were trees of small commercial value; 

 they were cut down by the root and left lying where they fell, 

 the branches not being removed. By the middle of April, all the 

 trees thus laid down were fully occupied by pairs of Pine 

 Beetles, and the traps had a very peculiar appearance, being 

 covered over with tiny heaps of bore-dust ; so numerous were 

 the breeding-tunnels, that many of the larvae perished from want 

 of food. 



The number of eggs in each tunnel were from 70 to 120, 

 the tunnels being 3 to 5 inches long. I found on an average 



1 Or " Hylurgus. " 



