192 PROTECTION OF WOODLANDS. 



attacked at all, it occurs to a far greater extent in avenues arid 

 clumps of ornamental trees in parks and gardens, than in the 

 close canopy of woodlands. But at the same time they do not 

 escape injury entirely. 



The broad-leaved species of forest trees that are most frequently 

 attacked, or rather that are least exempt from danger, are the 

 Elm, Ash, Birch, and in a less degree the Oak and Beech ; it is 

 also quite worthy of note that on the broad-leaved trees most 

 kinds of beetles are polyphagous, now attacking this, now the 

 other species. Here too, however, as among conifers, it is usually 

 the older stems of sickly growth that are most apt to be attacked. 



It is only young growth like seedlings, saplings, or poles and 

 older stems' that have been badly damaged, which are apt to 

 succumb soon to the injuries received ; for in tree-forest the 

 boring of the larvae may often be carried on for years before the 

 trees gradually show signs of dying off. Thanks to their strong 

 recuperative power, broad-leaved species of trees are altogether 

 less sensitive than conifers to wounds and injuries inflicted, 

 whilst at the same time a number of the bark-beetles that infest 

 the former class of trees live more in the wood than in the 

 cambium, and consequently threaten in a much less degree the 

 vital energy of the tree. 



The following include the more injurious species which are of 

 somewhat frequent occurrence : 



The Oak-beetle, Bostrichus (Xyleborus) dispar. This insect chiefly 

 attacks old Oak and Beech, that have been somewhat damaged or 

 interfered with in one way or another, and also bores into their 

 stools. Sturdy Oak saplings and transplants are often quickly 

 killed off in large numbers by reason of the galleries * formed by 

 the larvae within the slender stems. The cutting back of such 

 young growth, and the burning of the stems infested, are the 

 only way of annihilating this insect enemy. 



The variegated Ash-beetle, Hylcsinus fraxini, and the black Ash- 

 beetle, Hylesinus crcnatus, both live principally on the Ash. The 

 main gallery of the former consists of two horizontal arms or 

 branches, but that of the latter has only one. Here and there 

 these beetles occasion no inconsiderable amount of damage, as 

 poles and young stems of backward growth are often killed off 



1 They somewhat resemble the short galleries formed by Bostriclius (Xyl 

 lineatus in Spruce, but are very considerably longer (vide par. 71). Trans. 



