GARDEN INSECTS 



215 



the children shall spend the time on the phylloxera or on 

 some other form. 



The apple-root plant louse, or woolly aphid, of the apple, 

 ScJiizoneiira laiiigcra, is another important species. Like 

 the phylloxera it occurs in two forms. The one infesting 

 the bark may be found in pits and crannies about the 

 trunks and branches of apple trees ; it is a blue-black aphid, 

 the larger specimens covered with a bluish-white woolly 

 growth. The underground form causes warty swellings 

 on the roots. If an 

 apple tree becomes 

 sickly from no visible 

 cause, borers or the 

 like, its roots should 

 be carefully exam- 

 ined, and if the root 

 galls are found, it is 

 generally best to dig 

 it up and plant some 

 other kind of tree, 

 never an apple, in its place. Nursery stock that shows 

 these root galls should be rejected, or if this is not prac- 

 ticable, the roots should be soaked for half an hour in 

 water heated not above 150° Fahrenheit. 



Other species, too numerous to name, may be found on 

 the rose, apple, plum, peach, elm, maple, chestnut, oak, 

 and on many herbaceous plants. 



The Scale Insects, — Mealy Bugs, Scale Bugs, Bark Lice, — 

 resemble plant lice somewhat in their manner of life. As 

 their common names imply, they appear as scales on the 

 bark, leaves, and fruit of plants and, like the plant lice, 



Fig. 91. Woolly Aphids of Api'Lf. 



Showing characteristic swellings and cracks in the 

 bark which they cause. (Natural size) 



