DISEASES, INSECTS, AND ANIMALS INJURIOUS TO FOREST TREES. 281 



roots appear to be woven round with fine fungous filaments, in the 

 vicinity of which the bark tissues turn brown, whilst black pimples 

 about the size of a pin-head make their appearance here and there 

 on the main root. Wet weather is very favourable for furthering 

 the spread of this disease. 



Phytopthora fogi. 



This disease occurs chiefly on the seed leaves of beech, also on 

 those of the maple and sycamore : it makes itself apparent by 

 the blackening of the shoots and cotyledons, or by the breaking 

 out of black spots on these, which is soon followed by the death of 

 the seedlings. 



In.jukjoits Insects. 



Hylobiu^ abietis — Pine Weevil. 



The worst enemy to young conifers, especially after planting 

 out, is the Hylohhiii abietis, the large dark brown beetle of convex 

 shape, with light yellow marks between the eyes and on the 

 thorax and wing-covers. The weevils lay their eggs in spring 

 and continue to lay during summer, in dead but not dry pine, 

 choosing especially the cut stumps of recently felled trees, also 

 unbarked logs and the lower parts of dead standing trees. Under 

 the bark the grubs gnaw irregular galleries in the sap-wood, 

 changing at the end of these to pupa'. Like the grubs of all 

 weevil, they require shelter, and will not feed exposed to daylight. 

 They will, however, thrive in the closely-packed sawdust heaps 

 which accumulate while the wood is being sawn up, and which 

 serve excellently as a focus for infection. The duration of larval 

 life is very variable, and depends greatly on the temperature and 

 the season. As a rule, if the eggs are laid in the spring, the larvge 

 are seen in about a month, and are full grown by the autumn. 

 These full-grown larvti? lie in their hollowed-out beds until 

 the early summer of the next year, when pupation takes place, 

 followed by the issue of the adult beetles in June. The beetles 

 have a long life, and can continue egg-laying for a long time, so 

 that adults, puptB, larva% and eggs may all be got at the same 

 time. No injury whatever to growing plants of any value is done 

 by the feeding of the grub ; it is the work of the perfect beetle 

 which is so harmful. The insects can fly, but hardly ever do so, 

 except at pairing time ; they therefore frequent the neighbourhood 

 of their breeding-places. They prefer pine, but also attack spruce 

 and larch, hardly ever deciduous trees, unless pressed by hunger. 



VOL. XVII. PART II. T 



