162 
THE STUDY OF INSECTS. 
habit that the insects have of waving their bodies up and 
down, the plume-like masses of excretion rendering them 
very conspicuous. When an infested limb is jarred the 
Aphids emit a shower of honey-dew. Owing to the abun 
dance of this secretion, the branches and leaves of an infested 
tree become blackened by growths of fungi, as with the 
preceding species. 
The Woolly-louse of the Apple, Schizoneura lanigera 
(la-nig'e-ra), is one of the best-known pests of the fruit¬ 
grower. In its most conspicuous form it appears on the 
trunks and limbs of apple-trees, in clusters of individuals, 
which are conspicuous on account of the woolly excretion 
with which the bodies are covered. It is especially in* 
jurious to young trees, the bark of which becomes deeply 
pitted and scarred by its attacks. The bark apparently 
ceases to grow at the point of attack, but swells into a 
large ridge about the cluster of lice, leaving them in a 
sheltered pit. The lice also frequently congregate in the 
axils of the leaves and the forks of the branches. This 
species resembles the Grape Phylloxera in having a root- 
inhabiting form, which causes knotty swellings on the fibrous 
roots. It is the presence of this form that makes this 
pest such a difficult one to combat. For as it works deep 
in the ground upon the fibrous roots of trees, the same 
difficulties are met in attempting to destroy it that are pre¬ 
sented by the Grape Phylloxera. In fact, except in case of 
an especially valuable tree, we do not believe that it will pay 
to attempt to save a tree that has become badly infested 
by the woolly aphis. It will be cheaper to dig the tree up 
and burn it, and devote the ground to some other use. 
Another species of tree can be safely planted in the same 
place, but not an apple. Great care should be taken in 
putting out trees from a nursery to see that they are free from 
this pest. If there is any doubt the trees should be washed, 
roots and all, in a strong solution of soap. It is well also to 
put in the forks of the trees pieces of ha**d soars which will 
