176 INSECTS INJURIOUS TO FOREST TREES. 



one or other of them infests almost every species of tree and 

 shrub, when circumstances are favourable to their natui'e and 

 habits. Unlike the aphis and spider already mentioned, the 

 changes of climate and temperature in this country do not seem 

 to have much influence upon them. Most of the species which 

 infest trees and shrubs live through our severest winters un- 

 scathed, and ready to extend their devastations with renewed 

 vigour when genial weather sets in. They generally prefer to 

 attach themselves to the young bark and undersides of the leaves, 

 where they can easily penetrate to the sap upon which they feed. 

 When a tree is badly infested with them they cause great injury 

 to it, and if allowed to remain unmolested, they dry up the 

 bark, the tree becomes " barkbound," sickens, and ultimately dies 

 from the banefid effects of the scale. During my experience in 

 various parts of the three kingdoms, I have seen the oak, ash, elm, 

 beech, willow, poplar, silver fir, spruce, thorn, and hazel, besides 

 many varieties of shrubs, severely infested with scale of various 

 species, the trees assuming a dried up and stunted appearance, 

 leading to early decay, and deteriorating much from the value and 

 usefulness of the trees. Although we have many recipes for the 

 destruction of scale, none are thoroughly effective, except when 

 applied with an excess of care that can only be given to a limited 

 extent by foresters to some rare or valuable small specimen of tree 

 or shrub. I have found a mixture of one gallon of paraffine to 

 four gallons of water to be very efficient in getting rid of scale on 

 dry, hard bark, applying it with a stiff brush, so as to raise as 

 many of the scale as possible. This mixture must not be applied 

 to green wood or leaves, as it will kill them. The only safe plan 

 to clean young wood and leaves is to wash the scale off with a 

 sponge and soft water. Any other plan, or a mixture applied strong 

 enough to kill the scale, would certainly injure and probably kill 

 the leaves and green wood. Diluted spirits, turpentine, and train 

 oil, are recommended by some for killing scale. They will do so, 

 but ai*e very dangerous remedies, and ought never to be used 

 except with the greatest care, and by some one having a knowledge 

 of their strength and its effects. In regard to large trees and the 

 ordinary run of plants that come under the care of a forester, if 

 they are discovered to be infested with scale to any serious extent, 

 they ought to be rooted out and burnt, taking care that every 

 morsel of twig and bark is consumed that would afford shelter to 

 a single insect. The bark and twigs of all old trees that are cut 



