l62 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, ScJiizoneura 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 barl^ 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 hard soap, which will 



