HABIT8 AND LIFE HISTORY. , 37 
Very frequently the scale has a marked tendency to infest the extrem- 
ities of the branches and twigs. Tins is particularly noticeable with 
pear. As usually found on peach, the scale is massed often more 
densely on the older growth, and works out more slowly toward the 
new wood. 
The leaves are much less apt to bear scales, but in severe cases the 
upper surface particularly becomes infested, the scales frequently rang- 
ing in two or more quite regular rows on either side of the midrib. 
The male scales are more numerous on the leaves than the females. 
The infested leaves turn purplish brown. 
The San Jose scale Avas formerly supposed to differ from all others 
in the peculiar reddening effect which it produces upon the skin of the 
fruit and of tender twigs. This, however, sometimes occurs with other 
scales, but is a particularly characteristic feature of this insect, and 
renders it easy to distinguish. The encircling band of reddish dis- 
coloration around the margin of each female scale is very noticeable 
on fruit, especially pears. This appearance, however, sometimes so 
closely resembles the small spots on fruit produced by a common fungus, 
Entomosporium maculatum Lev., as to require close examination with 
a lens to distinguish it. Fruit severely attacked becomes distorted, 
rough, and pitted, frequently cracking, and may eventually fall prema- 
turely or at least become unmarketable. 
The cambium layer of young twigs where the scales are massed 
together is usually stained deep red or purplish, and when the scale is 
only scatteringly present the distinctive purplish ring surrounding each 
is almost as noticeable on young twigs as on fruit, and is of the greatest 
service in facilitating the inspection of trees which have been subject 
to possible contagion. The almost microscopic young scale might easily 
elude the most careful search, but the striking circling ring makes them 
comparatively conspicuous objects without the aid of a glass. 
If the tree survives the attack the infested wood eventually becomes 
knotty and irregular, partly from the sapping of the juices by the insect 
and also without doubt largely from the poisoning of the sap of the 
cambium layer by the punctures of the insect, as indicated by the dis- 
coloration. Young peach trees will ordinarily survive the scale only 
two or three years. Pears are sometimes killed outright, but generally 
maintain a feeble, sickly existence, making little or no growth for a 
somewhat longer period. 
food PLANTS. 
Practically all deciduous fruit trees are subject to the attacks of this 
insect, including also various small fruits, such as the currant, goose- 
berry, etc. It has also. been found on a great many shade trees and 
ornamental shrubs. The pear, peach, plum, apple, and cherry are 
almost equally liable to injury. The quince is apparently more rarely 
troubled. Notwithstanding its wide range of \'ood plants, certain 
varieties of pear, strangely enough, seem to be almost never attacked. 
