366 
Schwarz found this particularly true of the Duchess and Bartlett pears) 
along the midrib on the upper side of the leaf in one, two, or more 
quite regular rows, also to some extent along the side ribs, the male 
scales predominating over the female in such situations. The infested 
leaves turn purplish-brown, but do not have a tendency to fall. When 
occurring upon the fruit the scales have a distinctive peculiarity, in 
that they are invariably surrounded by a purplish discoloration of the 
skin of the fruit, and this discoloration is also noticed to some extent 
on the young growing twigs. The cambium layer of wood beneath the 
scales is stained purplish to some extent. In winter the scales upon 
a 
Fic. 26.—San José Scale: a, pear, moderately infested—natural size; b, female scale—enlarged. 
(From Circular No. 3, Diy. Ent.) 
twigs are difficult to distinguish. They lie close to each other, frequently — 
overlapping, and can only be differentiated with a magnifying glass. 
The general appearance which they present is of a grayish, very slightly 
roughened, scurfy deposit. The natural rich reddish color of the limbs 
of peach and apple is quite obscured when these trees are thickly 
infested, and they have then every appearance of being coated with 
lime or ashes. When the scales are crushed by scraping a yellowish, 
oily liquid will appear, resulting from the crushing of the soft, yellow 
insects beneath the scales. An infested pear is shown at Fig. 26 a, 
and an enlarged female scale at b. The appearance of an apple twig 
