Economic Importance of Animals 559 



producing very extensive damage. The leaf hoppers are difficult to 

 control, for they attack many types of plants. The rose leaf hopper is 

 a typical form which is very destructive of rose plants. Aphids (plant 

 lice) are small, very prolific Homoptera which attack a great variety of 

 vegetation. Some of the more common forms are the grape Phylloxera, 

 which causes decay by puncturing the roots of grapevines; the apple 



Fig. 289. — The lac insect (Tachardia lacca) of the order Homoptera. A, Piece 

 of twig encrusted with lac; at right the wormhke lac insects are shown in their 

 cells; B, young lac insect, greatly enlarged; C, body of an adult female lac insect 

 freed from its resinous secretions. (Modified from Green: Coccidae of Ceylon, 

 from Metcalf and Flint: Fundamentals of Insect Life, The McGraw-Hill Book 

 Co., Inc.) 



grain Aphid, which attacks the buds of apple trees, pear trees, haw- 

 thorn trees, as well as grasses and grains in warmer weather; the woolly 

 apple Aphid, which (Fig. 291) attacks the roots and branches of apple 

 trees. The cicadas are incorrectly called locusts. The 17-year cicada 



