176 



THE APPLE 



is accomplished through the agency of contact sprays applied 

 externally. Scale-extirpative measures are most successfully ap- 

 plied in the winter, for the reason that the trees are then dormant. 

 Powerful contact poisons, because of their strength and causticity, 

 cannot be used when the trees are in foliage. 



History. As the term " scale " suggests, the insects are pro- 

 tected by a waxy excretion under cover of which they feed and 

 breed. Save for a few hours after birth, during which they crawl 

 about, the females pass their entire existence under this covering. 



The males, after several 

 molts, leave the scale 

 casings as fragile two- 

 winged flies and enjoy 

 an ephemeral span of 

 liberty. In this brief sea- 

 son before death they 

 unite with the scale- 

 imprisoned females. 



The San Jose scale 

 passes the winter in the 

 half-grown stage under 

 the small, black, circu- 

 lar scales. Individual 

 scales are no larger than 

 the diameter of an ordi- 

 nary pin, and in small 

 numbers are so insig- 

 nificant as to be invisi- 

 ble to all save the eye trained to observe them. Very early in the 

 spring the males pupate, emerging soon after to unite with the 

 females, which by then have arrived at the proper stage for 

 complementary reproduction. In about three weeks or a month 

 the young of the first brood appear. These are borne alive by 

 the mother insect without an intermediate egg stage. Parturition 

 continues several weeks before the female dies. 



The newly born young, light yellow in color, crawl about several 

 hours before settling down in their fixed positions. The long 

 sucking tube is inserted into the tissues of the plant, and the 



Fig. 80. San Jose scale (enlarged). (Courtesy 

 of Ohio Agricultural Experiment Station) 



