Insects of Shade Trees and Their Control. rhe 
are then dormant and can withstand stronger sprays without injury. 
Summer spraying, when imperative, is most effectively done when the 
young are at the height of hatching, 1. e., crawling about in numbers. 
OYSTER-SHELL SCALE.” 
How injurious.—The oyster-shell scale lives and feeds on a great 
variety of shade trees, especially poplar, maple, birch, beech, and 
willow, besides hardy shrubs and certain fruit trees, all over this 
country, and though it occasionally kills an entire grown tree, it 
generally retards and stunts the infested growth and frequently 
causes the death of twigs and branches. 
How recognized.—The bark of an infested branch is found more 
or less densely crusted with brown or grayish, rather long, somewhat 
bent scales (fig. 55), wider at one end than the other, and sloughing 
off more or less readily. 
Fig. 55.—Oyster-shell scale on poplar. Much enlarged. (Quaintance and Sasscer.) 
Habits and seasonal history.—Shortly after the apple blossoms fall 
the eggs of the oyster-shell scale, which overwinter beneath the 
female scale, hatch into minute, licelike insects which craw] about for 
three or four days, and after inserting the threadlike beak, which 
serves as an anchor as well as a food conduit, into the host, settle per- 
manently on the bark. Thereafter the female never leaves the scale 
started by it when young, but ultimately lays its eggs and dies there. 
Control—Here and there an infestation by these scale-bugs is 
checked by minute, wasplike, parasitic insects that kill them. In 
most cases, however, spraying with lime-sulphur (p. 11-12) or a 
miscible oil (p. 12) must be resorted to for a prompt, effective 
remedy. The necessary preliminary work in preparation for spray- 
ing is indicated on pages 15-16. 
SAN JOSE SCALE.” 
How injurious.—For a series of years at the close of the last 
century the San Jose scale was the most dreaded insect pest of the 
4S Lepidosaphes ulmi lL... * Aspidiotus perniciosus Comst. 
