1908.] 



The Elm Bark Beetle. 



619 



tree, after removal of moss and the rough bark, for three 

 successive days till a crust is formed. If such a smear be used 

 it should be remembered that it will not act as a deterrent to 

 boring by the adult beetle unless it is laid on some millimetres 

 thick." 



Mr. Cole, Forester at Letch worth, has also supplied the 

 following report on the steps taken by him to destroy the 

 beetle : — 



" When I first commenced work at Letch worth, I noticed a 

 bad attack of Scolytus in Spring Wood. The worst of the trees 

 were at once taken out and destroyed. Three years ago, I 

 noticed many trees on the exposed side showed signs of disease 

 and I commenced to take out the affected limbs. Acting on 

 experiments I had seen in Central and Western Europe, I 

 also endeavoured to cause a sudden flow of sap and thus 

 drive out the beetles. This flow was encouraged by severely 

 pruning the lower limbs and dressing the wounds to prevent 

 bleeding, and on the trees thus treated it was noticed that 

 the burrowing females were driven to the entrance of their 

 burrows and were forced to remain there owing to the flooded 

 workings. Whilst in this state they fell an easy prey to the 

 common wasp which swarmed over the trees, dragged out the 

 beetles and devoured them. The wasps were so plentiful 

 that I had many complaints of wasp nests in the trees. The 

 larvae were trapped in their own burrows, being unable to 

 return owing to the early part of the burrows being too narrow 

 for their increased size. Examination of larvae thus entrapped 

 showed them to be a dull iron red and surrounded by a viscid 

 substance which proved to be partly sap and partly a secretion 

 from the larvae. The secretion was unlike that usually met 

 with at this stage. 



" The summer of 1906 was very dry here, and, added to this, 

 the sub-soil was drained by the cutting of sewers, gas and water 

 mains, &c. Where the soil has been thus drained, making it 

 in consequence impossible to keep the burrows flooded, pupa- 

 tion took place and the beetles returned to the weakened trees 

 and killed them. 



" By carefully caging portions of affected bark I found the 

 beetles came to the surface in June and commenced to burrow 

 again within three days. By cagings on young and vigorous 



