APPLE INSECTS 



177 



pear and apple orchards in the northeastern portion of the 

 United States, and its range now includes most of Canada and 

 the United States ; it has been introduced into England. It 

 is often so abundant as to nearly cover the bark of apple, pear, 

 currant, black raspberry, Japan quince and mountain ash, 

 sometimes killing these plants, but usually it is not very destruc- 

 tive. Its different food-plants now number nearly twenty-five, 

 including the peach and quince, besides the fruits just mentioned. 

 Usually the bark only is infested by this scurfy scale, but rarely 

 it gets on to the fruit and causes similar but larger reddish dis- 

 colorations of the skin than the San Jose scale (Fig. 176). 



Fig. 175. — Apple branch infested with the scurfy scale. 



The rather flat, somewhat pear-shaped grayish-white female 

 scales are about ^ of an inch long and when numerous give the 

 bark an ashy or scurfy appearance, whence the common name 

 (Fig. 175). The scale consists of the two minute cast skins at 

 the smaller end and a large, broad, thin, whitish portion secreted 

 by the yellowish grub-like female insect beneath, and is, there- 

 fore, easily distinguished from the narrower, more convex, dark 

 brown oyster-shell scale. The male scurfy scales are much 

 smaller than the females, brilliantly white in color, with 

 nearly parallel sides, three longitudinal ridges or keels, and 

 a single conspicuous, yellowish-brown cast skin at the end 



