62 
The Cottony Maple Scale 
(Puk'inaria litis Linn.) 
The cottony maple scale (Fig. 64) is one of the best known 
scale insects because it heavily infests se\eral very common shade 
trees, and because the cottony masses beneath the body of the adult 
female in early summer make it a very conspicuous object. These 
large white masses are a deposit of waxy threads within which are 
the minute, oval, pale yellowish eggs. 
The history of this insect in Illinois since 1867 exhibits suc- 
cessive periods of abundance and of scarcity, each averaging about 
four or five years for the state as a whole. That is, thruout 
some considerable part of the state, and often over most of it, 
the maple scale has been injuriously abundant once in eight or ten 
years, and its period of abundance has lasted, as a rule, about half 
this time. In any given locality, however, it has usually been in- 
jurious for a much shorter time, often for not more than one or two 
years. The cessation of its injuries and its virtual disappearance 
from the trees infestefl by it have seemingly been due almost wholly 
to the agency of its insect enemies. 
The soft maple {Acer saccJiariiiiini) is the tree most generally 
and heavily infested by this insect. The hard maples, on the other 
hand, are infested but slightly if at all. The box-elder is also greatly 
subject to injury, and next to this, perhaps, the linden or basswood. 
Among the other trees and woody plants often more or less injured, 
are the elm. honey-locust, black locust, black walnut, sumac, willow, 
poplar, beech, hawthorn, bittersweet, grape-vine, and Virginia creep- 
er. We have found mature egg-laying females on the horse-chest- 
nut, honeysuckle, dogwood, trumpet-creeper, mulberry, snowberry. 
smoke-tree, Spircca. false syringa { Fliiladclphiis) , and Wistaria. 
Oak. ash. and catalpa are not infested in northern Illinois, but injury 
to oaks is reported ironi Georgia. The pear is said to be most liable 
to injury among the fruit trees, and apple, plum, and peach are 
sometimes infested. Serious damage to fruit trees is, however, very 
unlikely. The migrating young. \\ hich are often w'ashed from trees 
by rain, or blown off in considerable numbers, may maintain them- 
selves for a time on a great variety of woody and herbaceous plants, 
those on the latter, of course, perishing with the advent of frosts. 
In early summer this scale, when very abundant, coats the under 
side of heavily infested limbs with a thick layer of cotton-like waxy 
masses, each projecting from beneath a brown cap or scale — the 
flat body of the mature female. This "cotton" is secreted and the 
eggs are deposited within it in late May or early June in the latitude 
of central Illinois, but usually one or two weeks later in the Chicago 
district. 
Something over 3,000 eggs are usually laid by each female, the 
nuirlber ranging, in our counts, from 2.856 to 3,863. with an average 
