32 



the spring those which are alive begin sucking the sap, and about 

 the first of June become adult. Reproduction now begins, the 

 young being born alive at the rate of three or four or more nearly 

 every day for about a month, after which the parent dies. By this 

 time the first-born young are now adult and beginning to produce 

 young, however, so that young scale insects may be found at almost 

 any time from about the fifteenth of June till winter stops their 



Fig. 1. — San Joee scale: a, twig showing scale, natural size; h, portion of bark showing 

 crawling young and scales in various stages. (Howard and Marlatt, Bull. 3, N. S., Div. of 

 Ent , Dept. of Agr.) 



production, though they are more abundant at certain times during 

 this period than at others. 



That an increase in this wa}' must result in the production of an 

 enormous number of new scales is evident. It has been calculated 

 that if all tlie progeny of a single female which begins breeding in 

 June should survive and reproduce in their turn, the number of 

 female descendants of this female when winter stops reproduction 

 would be 1,608,040,200, and while this is never the case, it is 

 not strange that with even a small proportion of this number of 

 insects sucking the juices from the plant severe injury should 

 ensue and often cause its quick death. . 



