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Insects of Shade Trees and Their Control. 83 
the trees, but it is often so very injurious, especially to young stock, 
that, together with the injury caused by the elm leaf-beetle, another 
importation from Europe, attack by bark-borers, etc., is induced 
and the trees do not recover. 
How it lives and looks.—This scale spends the winter in crevices 
of the bark on the trunk and larger branches as brown immature 
males and females embedded in 
white cottony matter (fig. 59). 
On the appearance of warm 
weather, in May at Washing- 
ton, D. C., these forms begin 
to move about, molt, and mate, 
after which the females attach 
themselves permanently on 
limbs and trunk. The young—clear, lemon-— 
yellow, lice-like insects—issue during June and 
July, settling temporarily on leaves alone or on 
leaves and twigs, depending on the smoothness of 
the latter. In August they return to the larger 
branches and trunk to settle for the winter, thus 
completing in Washington the seasonal life cycle. 
Iemedies.—In the case of shade trees and nur- 
sery stock the best means of killing this insect is 
to spray infested trees during the dormant season 
with a water solution of miscible oil (p. 12) or 
kerosene emulsion (p. 12-13). Spraying with 
summer strengths of these preparations while the 
young are hatching is the next best means of 
control. Other means are available, such as water 
applied with a hose under high pressure, but none 
of them is as satisfactory as spraying with the 
solutions mentioned. 
APHIDS IN GENERAL. 
Evidence of infestation—During the growing 
season aphids or plant-lice occur in winged and rye, 59,—Buropean 
wingless form in greater or less numbers on eve scale. Mature 
. = females. (Photo- 
branches, twigs, and leaves. They feed on the sap, graph by Sand- 
which they suck up from within the tissues by pane 
means of their pointed beaks, hence are classed as sucking’ insects. 
Unider favorable conditions aphids suddenly appear in great num- 
bers, particularly in the spring. Their presence is indicated by an 
abundance of sticky “honeydew” on and under the infested plants, 
by the presence of ants which feed on the honeydew but do not harm 
