24 



the first born of a female may be ready to become mothers before the ' 

 original female has ceased to reproduce. 



Keproduction continues throughout the summer, and a single pair, 

 starting in June, may become the ancestors of over one thousand 

 million examples before the season closes. Eeproduction is most 

 active early in September, and throughout that month larvae occur in 

 abui)dance on infested trees. It is the season at which spread is 



a. Z 



Fig. 13. 



The San Jose scale : a, on a twig, natural size ; h, as seen under a hand lens, much enlarged. 

 Dir, Ent., x;. B. Dept. Agl. 



most general and the agents of that spread are birds and other in- 

 sects that visit the infested trees. The crawling larvae get upon any- 

 thing, including the backs of beetles and the feet of birds, and are 

 carried for considerable distances, causing outbreaks where none 

 had been looked for. An insect that attacks so many different 

 kinds of plants,' that breeds so abundantly, and that has no natural 

 enemies to keep it in real check, is, of course, a pest of the first class ; 

 and so all gardeners have found it. 



