INSECTS AFFECTING CITRUS FRUITS 459 



as it feeds among them. The larvae of lace-wing flies and 

 syrphus-flies also destroy many mealy-bugs. 



The Cottony -cushion Scale (Icerya purchast). This insect 

 was at one time the most serious pest of the citrus fruits in 

 California where it destroyed many groves of citrus trees and 



FIG. 219. Cottony-cushion scale, Icerya p2irchasi, on orange tree. A 

 few young are seen on the white egg sacs. (About natural size; after 

 Quayle, photo by Doane.) 



many ornamental plants. It has not appeared in destructive 

 numbers in other parts of the United States. It was intro- 

 duced into California from Australia about 1868, and within 

 ten years had become very abundant and destructive, particu- 

 larly in the southern part of the state. For some years the 

 orange and lemon growers fought against it unsuccessfully. 



