As we look at living creatures much smaller than ourselves, many of us imagine that they must lack the organs and functions that we have. how can something as tiny as an insect have a heart? how can it have a circulatory system and blood in its tiny body?
but the miracle of life is not only that these creatures have organs, but that these organs are perfect for each insect’s way of life.
adult insects have bodies with three sections; head, thorax, and abdomen. the head has a pair of antennae in front that are feelers, and that usually have some tiny organs of smell. the eyes and mouth are part of the head, too.
not only does an insect have a heart, but it also has blood and a circulatory system. the blood passes into the heart by means of holes equipped with valves. when the heart contracts, these holes close, and the blood is driven out through the arteries. insects don’t have a system of capillaries and veins as we do.
the reason their circulatory system is not greatly developed is that they don’t depend on the circulation of the blood for their supply of oxygen. in our bodies, as you know, the blood carries oxygen to every part and enables it to function.
but insects have a different system of breathing. they have tiny branching tubes that end in little air holes in the sides of the body. the air comes in right from the surface of the body and goes directly to the cells.
a more complicated system would be too much for their size. on the other hand, a simple system like theirs wouldn’t be enough for larger animals. it’s not too bad a system, though, considering that more than half of all living animals have it.
did you know that one name for an insect is hexapod? the term is from two greek words meaning six and foot. if you count the feet of an insect, you can see why hexapod is a good way to describe most insects. the legs are usually in three pairs, and are attached to the thorax.
there are thousands and thousands of different species of insects, among them some of man’s best friends as well as some of his worst enemies.