204 Practical Forestry 



white with yellowish-brown veins, a row of rounded bluish 

 spots running between every two. 



By stuffing a piece of tow in gas tar, or placing cyanide 

 of potassium in the hole and closing the aperture, the cater- 

 pillar may be overpowered and destroyed. 



A bent wire has often been successfully used in dislodg- 

 ing the caterpillar. 



The Holly Fly (Phytomyza aqui folia). The foliage of the 

 holly is frequently very much disfigured by the grubs of the 

 holly fly, which burrow beneath the upper skin of the leaves, 

 feeding on the internal substance. This imparts a blistered 

 and discoloured appearance, which, in the case of ornamental 

 varieties, is anything but desirable. Probably no great 

 damage to the infested trees is brought about, but the whole- 

 sale destruction of the leaves, as is often the case, cannot 

 but weaken the plant. 



In May and June the flies make their appearance, and lay 

 their eggs beneath the upper skin of the leaf, from which 

 the grubs, about one-fifth of an inch long, are hatched. 

 These work their way beneath the skin of the leaves, form- 

 ing small tracks of a more or less circular shape, thus causing 

 the large and unsightly blisters. They quit the leaves 

 about March, by making small holes in the skin of the leaf, 

 and afterwards become chrysalides. The fly is small and 

 inconspicuous. 



Picking off and destroying affected leaves, or crushing 

 the grub by pinching the blisters are the only ways of lessen- 

 ing the attacks. 



The Oak Leaf Roller Moth (Tortrix viridana).The 

 widespread destruction caused to oak-woods in almost every 

 part of the country by the caterpillars of this little moth 

 would seem to be on the increase from year to year. But 

 it is not the oak .alone that suffers, for numbers of the horn- 

 beam and beech are in an equally pitiable condition. Hav- 

 ing closely watched this insect for several years, mainly 

 with the view of striving to keep it in check or devise some 

 means of destruction, I have come to the conclusion that a 

 few individual trees may, at considerable expense, be rid 

 of the pest, but in the case of whole woodlands artificial 



