INSECTS 



i/7 



formation of the scale begins. This, at first, is white, but changes 

 in color through successive molts to gray or black. 



Each circular scale is surmounted at the apex by a nipple. In 

 the elongated males the nipple is also present, but near the anterior 

 end. The conformation of this nipplelike marking is characteristic 

 of the San Jose scale and differentiates it from other species which 

 otherwise outwardly resemble it. The size of both sexes materially 



FlG. 8l. Result of scale injury 



Trees which had to be dehorned owing to the work of the San Jose scale. (Courtesy of 

 A. 1.. Stene, Rhode Island) 



increases with age, and the male assumes an elongated shape. 

 Each generation requires from thirty-three to forty days from the 

 emergence of the larvae of one brood to the emergence of the 

 larvae of its progeny. The average period of oviposition of a female 

 being about six weeks, there is consequently a well-defined over- 

 lapping of summer broods. 



Since the female never leaves its scale covering, it is evident 

 that the spread of the insects from one plant to another and from 



