INSECT ENEMIES OF CITRUS FEUITS. 



13 



a month later inspections were made throughout the lower San Gabriel 

 Valley, at Pomona, Ontario, and Riverside, and in Orange County. 

 Throughout this valley a large majority of the young insects which had 

 hatched were dead at this time while fully 50 per cent of the eggs had 

 dried up. At Pomona, Ontario, and Riverside almost all the young 

 insects had been destroyed, and fully 90 per cent of the eggs beneath 

 the old scales. In Orange County near the coast a very small per- 

 centage of eggs was affected by this hot period, while recently hatched 

 young scales were much in evidence. The black scale occurs en a 

 wide range of hosts, including trees, shrubs, and herbaceous plants. 



The red scale (fig. 5) thrives exceedingly well in the drier interior 

 regions of southern California. It can be found within a few miles 



Fig. 5.— Leaves and branch of orange infested with red scale {Chrysomphalus aurantii). (0ri::;inal.) 



of the ocean or as far inland as Redlands. The limits cf its distri- 

 bution are rnuch the same as for the black scale. This species can 

 be found on several host plants other than citrus species. 



The yellow scale is even more of a heat-withstanding form than 

 the red scale. Infestation by this insect appears to be most marked 

 in the foothills region of the San Gabriel Valley, and along the Sierra 

 Madre Range through Upland and Cucamonga. It is also broadly dis- 

 tributed at Redlands, where it has become a more serious menace than 

 elsewhere in southern California. That it is capable of withstanding 

 excessive heat is demonstrated b}^ its prevalence in citrus orchards 

 in the San Joaquin Valle}-, at Marysville, Oroville, and other parts of 

 the hot interior valleys of northern California, where the purple scale 

 and to a large extent the black scale appear unable to survive. 



