day,
and so continues for two years, probably laying no less than 40,000,000
eggs. In one summer the bluebottle fly could have 500,000,000
descendants if they all lived. The plant louse, at the end of the fifth
brood, has laid in a single year enough eggs to produce 300,000,000
young. Of course every one knows that, owing to enemies and diseases
(for the insects have enemies which prey on them just as they prey on
plants) comparatively few of the insects hatched from these eggs live
till they are grown.

[Illustration: FIG. 146. A BUTTERFLY PUPA
Note outline of the butterfly]

The number of insects which are hurtful to crops, gardens, flowers, and
forests seems to be increasing each season. Therefore farm boys and
girls should learn to recognize these harmful insects and to know how
they live and how they may be destroyed. Those who know the forms and
habits of these enemies of plants and trees are far better prepared to
fight them than are those who strike in the dark. Moreover such
knowledge is always a source of interest and pleasure. If you begin to
study insects, you will soon find your love for the study growing.

[Illustration: FIG. 147. THE GROWTH OF A GRASSHOPPER]

=EXERCISE=

Collect cocoons and pupae of insects and hatch them in a
breeding-cage similar to the one illustrated in Fig. 149. Make
several cages of this kind. Collect larvae of several kinds; supply
them with food from plants upon which you found them. Find out the
time it takes them to change into another stage. Write a
description of this process.

The plant louse could produce in its twelfth brood
10,000,000,000,000,000,000,000 offspring. Each louse is about one
tenth of an inch long. If all should live and be arranged in single
file, how many miles long would such a procession be?

[Illustration: FIG. 148. PLANT LICE]

[Illustration: FIG. 149. CAGE IN WHICH TO BREED INSECTS
Flower-pot, lamp-chimney, and cloth]

SECTION XXXII. ORCHARD INSECTS

=The San Jose Scale.= The San Jose scale is one of the most dreaded
enemies of fruit trees. It is in fact an outlaw in many states. It is an
unlawful act to sell fruit trees affected by it. Fig. 150 shows a view
of a branch nearly covered with this pest. Although this scale is a very
minute animal, yet so rapidly does it multiply that it is very
dangerous to the tree. Never allow new trees to be brought into your
orchard until you feel