Packard.] THE POPULATION OF AN APPLE TREE. 171 
attached to the insect as at 4. By the first of August the 
growth of the scale insect is completed, and it has the 
appearance of an oyster shell, as seen at 7. By the middle 
of August in the western states, where Mr. Riley studied 
its habits, the female lays her eggs, which do not hatch till 
the following June. It will be seen that the best method 
of warding off the attacks of this pest is to thoroughly 
scrape the bark of the tree in the early autumn and again 
in the beginning of June, when the young are swarming 
over the surface of the bark. At this time the bark should 
be washed with whale oil soap. But it is to the natural 
insect parasite when reared and set loose in the orchard 
that we are to look for the means of restraining within 
proper limits this insect. This is the minute ichneumon fly 
(Aphelinus) figured on page 42. 
The majority of the insects injurious to the apple-are found 
FEEDING ON THE LEAVES. 
The American Tent Caterpillar , or Clisiocampa Americana , 
is known to every farmer’s boy from the social habits of the 
caterpillar, which lives protected from the hot sun or inclem¬ 
ency of the weather under a broad tent of white silk. Not 
very creditably to orchardists and farmers they are a con¬ 
spicuous object at the beginning of summer, whether in the 
New England, Western or Middle states. The caterpillar 
is easily recognized by its large size, being about two inches 
in length, and by the long brown hairs and bright colors 
of the body, which is yellow with numerous fine crinkled 
black lines, forming low down on the sides of the body 
a black band, with a blue spot on the side of each ring. 
Along the middle of the back is a conspicuous white stripe. 
It becomes fully grown by the first or middle of June, the 
period varying with its geographical position. When about 
to make its cocoon it stops eating, and wanders restlessly 
about in search of a suitable place in which to spin. Under 
11 
