276 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



A third enemy of Hylesinus pini]Jerda, and also a useful 

 assistant in destroying large numbers of weevils and beetles in 

 the grub stage, is the squirrel, by whom we were frequently 

 guided to standing fir tree3, which, though they had green tops, 

 were infested with grubs of beetles and weevils. The squirrel 

 found the grubs in the upper part of the trees, where the bark 

 wa3 not over one-fourth of an inch in thickness, and where they 

 pass through the pupal stage, buried between the bark and the 

 wood. Where the bark is over a quarter of an inch in thickness, 

 the grubs of both beetles and weevils, when full fed, retire into 

 it, and there the squirrel cannot get at them. I think that 

 the squirrels would not feed on grubs unless they were short 

 of other food ; and in support of this opinion I may say that 

 from 1895 to 1899, when I observed them eating grubs, Scotch 

 fir cones were not to be found in this district. Although the 

 squirrel has been of some use in destroying beetles and weevils 

 from 1896 to 1899, I sincerely regret that at the same time they 

 do serious damage to young Scotch fir woods in parts of Scotland. 

 In this district, however, they have been kept well under, and 

 I have not seen so much as one fir tree peeled by the squirrel. 



During the past summer, we have again, by means of trap 

 trees, destroyed a great many beetles ; but they are now greatly 

 reduced in numbers, and many of the injured fir trees have, 

 during the past summer, made normal growth. 



In the course of my operations against the Pine Beetle, I have 

 had the opportunity of studying the habits of other beetles and 

 insects that do damage to our Scotch fir woods, such, for example, 

 as the Crutch Beetle (Hylesinus palliatus), Bostrichus bidens, the 

 two-toothed beetle, which is one of the smallest of the tribe, and 

 Bostrichus lineatus. I have also found specimens of another beetle 

 enemy, viz., Glerus formicarius. The Giant Wood Wasp (Sirex 

 gigas) and the Steel Blue Wood Wasp (Sirex juvencus) do serious 

 damage to felled timber, rendering it almost useless; but I have 

 not known either to attack a healthy growing tree. 



Dr R. Stewart MacDougall, the Honorary Consulting Ento- 

 mologist of the Society, has been my tutor and guide in the 

 operations I have carried out during the past four years. I 

 worked out many of his suggestions, and have found them to be 

 most effectual. The assistance I have received from him is indeed 

 one of the greatest benefits I have enjoyed from my connection 

 with the Society. 



