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 (I eery a 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 purchasi, 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. 



