No. 4.] 



SAN JOSE SCALE. 



301 



average, these gentlcmeu find that in the course of a single 

 summer one female might become the parent of over three 

 billion progeny. When one contemplates the remarkable 

 rapidity with which this insect multiplies, — a brood of 

 about four hundred every six weeks, — what wonder is it 

 that in the space of two or three seasons this prolific pest is 

 able to spread over even large fruit trees? The lapping over 

 of the different generations is one of the greatest hindrances 

 to the successful use of insectides against this insect. With 

 many of our scale insects the young appear at known inter- 

 vals of time, and the use of a suitable contact insectide at 

 the proper time will insure the destruction of the whole 



Fio. 2. Scurfy bark louse (Chionasj>i-i fur/urns): a, c, females; b, d, males; a, b, 

 natural size; c, d, enlarged. From Howard, Year Book, U. S. Department of Agri- 

 culture, 1894. 



brood. Not so with the San Jose scale. Such a wash, to 

 be effective, would need to be repeated daily for perhaps six 

 weeks in order to destroy the young born at different 

 intervals. 



The two scales most commonly met with in the orchards 

 and nurseries of the State are the scurfy bark louse and the 

 oyster-shell bark louse, and these two insects are the ones 

 most frequently mistaken for the San Jose scale. The figures 

 given so well illustrate the characteristics of these scales that 

 detailed description is unnecessary. The scurfy bark louse 

 (Fig. 2) is common on trees of the apple family and on 

 currant bushes. It is compact, slightly elongate, thin, and 



