entirely unsheltered like the pupa of the elm leaf beetle. After the
pupa stage comes the _adult insect_, which may be a moth or a
beetle.

A study of the four stages of any particular insect is known as a
study of its _life history_. The important facts to know about the
life history of an insect are the stage in which it does most of its
feeding, and the period of the year in which this occurs. It is also
important to know how the insect spends the winter in order to
decide upon a winter treatment.


IMPORTANT INSECTS


THE ELM LEAF BEETLE

Life history: The elm leaf beetle, Fig. 100, is annually causing the
defoliation of thousands of elm trees throughout the United States.
Several successive defoliations are liable to kill a tree. The
insects pass the winter in the beetle form, hiding themselves in
attics and wherever else they can secure shelter. In the middle of
May when the buds of the elm trees unfold, the beetles emerge from
their winter quarters, mate, and commence eating the leaves, thus
producing little holes through them. While this feeding is going on,
the females deposit little, bright yellow eggs on the under side of
the leaves, which soon hatch into small larvae or grubs. The grubs
then eat away the soft portion of the leaf, causing it to look like
lacework. The grubs become full grown in twenty days, crawl down to
the base of the tree, and there transform into naked, orange-colored