10 



CIRCULAR 2 7 0, U. S. DEPARTMENT OF AGRICULTURE 



varieties of fruit trees. Many of these plants or trees grow in the 

 gardens or about the houses in fruit-growing districts, and unless 

 they are regularly inspected and are sprayed, if infested, they are 



very likely to be trouble- 

 some centers of infestation 

 for nearby orchards. 



LIFE HISTORY 



The San Jose scale re- 

 mains in one place during 

 most of its life. In the fall 

 practically all stages may 

 be found on the trees, but 

 only those that are about 

 half grown survive the win- 

 ter, and in severe winters 

 many of these succumb. 

 Temperatures of —15° to 



— 20° F. cause a mortality 

 of approximately two thirds 

 of the half-grown scales, 

 and 90 percent or more are 

 killed if the temperature 

 gets as low as —25° or 



— 30°. In the spring the 

 scales that have survived 

 continue their growth and 

 mature in May or June. 

 The males develop wings 

 and are active, although 

 they do little flying. The 

 females have no wings, re- 

 maining where they have 

 developed and producing 

 several hundred very small, 

 louselike, yellowish, active 

 young. These young are 

 capable of crawling consid- 

 erable distances during the 

 first few hours of their lives, 

 and spread about at that 



time. During their period of activity they are often carried to other 

 trees by the wind, on the feet of birds, on the clothing of men working 

 in the orchards, or on horses or farm implements. They ordinarily 

 settle down within a few hours on the bark or on leaves or fruit, insert 

 their long, threadlike beaks into the plant tissue, and commence feed- 

 ing. Almost at once they begin to secrete a waxy material which soon 

 forms a characteristic, circular, scalelike covering. The covering of 

 the female when fullgrown is about the size of a pinhead, grayish, with 

 a dark, central, nipplelike projection, while that of the male is some- 

 what elongated (fig. 8) . If these coverings are turned over, the deli- 

 cate, bright-yellow, saclike bodies of the insects may be seen. Growth 

 is completed in about 6 weeks, and there are two or more generations 

 in a season. 



Figure 7. — Bark encrusted with the San Jose 

 scale. X 5. 



