312 Studies in Forestry [CHAP. xiv. 



Curculionidae), or else hollow out the pith from young shoots 

 (e. g. some Hylesinini and Tortriddae}. 



Leaf-destroyers, including the caterpillars of most moths 

 (Lepidopterd) and Saw-flies (Tenthredinidae), also leaf-beetles 

 (Chrysomelidae), cockchafers (Melolontha\ and Spanish fly 

 (Lyttd). 



In addition to these main groups, there are also Bud- 

 destroyers, consisting of several weevils {Curculionidae} and 

 some leaf-roller caterpillars ( Tortriddae}, Seed-destroyers like 

 the acorn-borer (Balaninus) and the larvae of Grapholitha 

 strobilella and species of Anobium in Spruce cones, and also 

 Producers of hypertrophic Deformities and various Mal- 

 formations on foliage, shoots and fruits by gall-wasps (Cyni- 

 pidae}, gall-midges (Ceddomyidae), plant-lice (Aphidae), which, 

 though frequently more easily noticeable, are as a rule in 

 reality of such comparatively trifling physiological and technical 

 consequence that they may almost be left unnoticed. 



Although a biological classification according to the ages 

 of the crops attacked seems less preferable than that above 

 sketched, it may nevertheless be remarked that most weevils 

 or rostral-beetles (Curculionidae), some leaf-rollers (Tortriddae}, 

 and the grubs of the cockchafer (Melolontha] genus of the 

 lamellicorn beetles (Scarabidae] usually attack seedling growth 

 and young plantations; whilst crops that have outgrown the 

 thicket stage and have developed into pole-forest or tree-forest 

 are most exposed to attacks from the majority of species of moths 

 ( Lepidoptera\ and then of the many bark-beetles (Bostrychini} 

 and cambial-beetles (Hylesinini} which follow in their wake 

 when once physiological disturbances have been occasioned 

 and the young trees grow sickly in consequence. Many moths, 

 however, exhibit an unquestionable amount of choice between 

 pole-forest and tree-forest in commencing to feed. Thus, for 

 instance, the caterpillars of the Pine owlet-moth (Trachea pini- 

 perda} and the Pine Span-worm (Fidonia piniaria} are always 

 to be found in pole-forest crops first of all, whence they migrate 



