DAMAGE CAUSED BY ANIMALS. 129 



As regards the clearance of timber crops that are already nearly 

 mature, there will, of course, be less hesitation or delay than in 

 the case of younger crops ; hence all the older falls of timber that 

 have been essentially injured in annual increment may be cleared. 

 But when the devastation has been committed over extensive 

 areas, so that the utilisation of the trees is likely to affect the 

 market price of the timber very prejudicially, endeavours will 

 naturally be made to perform the operation of clearance as gradu- 

 ally as possible ; in this matter, however, prudence must dictate in 

 regard to the previously-mentioned dangers of sickly crops from 

 other enemies among the Scolytidsz and Curcidionidm. 



But whatever timber it is considered necessary to fell should 

 be prepared for sale as speedily as possible. Both long timber and 

 fuel should be barked in order to let it dry quickly, and all fuel 

 should be well split ; and finally, all the wood, of whatever class 

 or assortment, should be stored or stacked in airy places, and well 

 raised from the ground on suitable rests. 



63. Classification of the injurious Forest Insects. 



The injurious forest insects may be grouped together in many 

 different ways, either according to the parts of the tree they 

 damage, or according to the manner in which they injure the vital 

 power and the value of the tree, or according to the age of the 

 woodland crops chiefly attacked by them, or according to the 

 degree and extent to which they do injury. Again, they may, of 

 course, also be classified according to the species of tree on which 

 they chiefly occur, or simply in accordance with their natural 

 entomological classes. 



According to the portions of the tree attacked by them, they 

 are grouped into 



1. Wood-boring or Timber-destroying insects, which either bore 



into and riddle the wood with holes (e.g., some Scolytidte, 

 Cerambycidte, Siricidse), or destroy the cambial layer of the 

 bark and the sap wood (e.g., Bostrichini and several Curcu- 

 lionidai), or eat out the pith from the tender shoots (e.g., 

 some Hylesinini and Tortricidte). 



2. Leaf-destroyers, including the caterpillars of most Lepidoptera 



and of Tenthredinidte, cockchafers (Melolontha), leaf-beetles 

 (Chrysomelidte), and Spanish fly (Lytta vesicatoria). 



