4-H CLUB INSECT MANUAL 3 
threaten our plants and animals. Some of the diseases carried only 
by insects have killed more people than have been killed in all wars. 
However, to give the impression that all insects are pests would be 
unfair, for most of them are of little or no importance and many, 
such as the ground beetles, ladybeetles, wasps, and certain flies, are 
beneficial, as they feed on insect pests. The honeybee makes honey 
and beeswax, the silkworm makes silk, and many insects pollinate 
plants. Insects also provide food for birds and fishes. 
This manual has been prepared so that young people may have a 
better understanding of the lives and habits of many of the insects 
and why they have been able to exist for so many centuries. Re- 
member that even an insect may be justly entitled to a living and 
do not destroy one wantonly or without good reason. We must, how- 
ever, be able to protect ourselves against their taking too much of the 
material we claim. The more of us there are who know our friends 
and foes in the insect world, the better we shall be equipped to stand 
our ground against the ravages of our greatest rivals, the insect pests. 
Part I—ACQUAINTANCE WITH INSECTS 
[Introduction to first-year work] 
What is this creature we call an insect, and how does it differ 
from other forms of animal life? Insects are animals that in the 
adult stage have an external skeleton and three definite body regions, 
the head, thorax, and abdomen. They have three pairs of legs and 
only one pair of antennae (feelers). They usually have compound 
eyes and one or two pairs of wings. 
aa AEM OC = 
\Head 
| thorax 
Abdomen 
Ficure 1.—External construction of an insect. 
Insects are adapted to a wide range of conditions. Some live 
in the air and soil, some in plants or animals or their products, 
and some in the water. Those that live out of the water breathe 
through small openings along the sides of their bodies, and some 
of those that live in the water are equipped with gills which enable 
them to get their air from the water. 
There are more kinds of insects than of all other forms of animal 
life put together. In fact, an entomologist found more than 1,000 
different kinds in his small back yard in a suburb of New York City. 
As there are about 700,000 different kinds of insects known to exist, 
the need for some form of classification becomes apparent. Entomolo- 
gists separate them into orders, families, genera, and species. (Each 
of these classifications further divides the one preceding.) In this 
manual no more can be done than help to acquaint the reader with 
the more common orders. 
