My favorite TV Channel is the Shanghai Documentary Channel, because I can always enjoy the graceful creatures on it. I’ll intrude one kind of creatures today, insect.
First, let’s think about what is an insect? Is the butterfly an insect? Is the spider an insect?
Insect is belonged Arthropoda (节肢动物门). So, an insect must have all the characters of the Arthropoda. An arthropod has the following features: First, its body can be separated into several segments. Second, it has legs, which can also be separated into several segments. That’s why we call it 节肢动物. Now we know neither the earthworm nor the snail is an Arthropod, because the have no legs. Is our human being an Arthropod? We have legs. But no! An arthropod has bones covered outside of its body, but our bones are inside of our bodies. Ok, lets count how many arthropods we know. The shrimps, the crabs, the spiders, the butterflies, the bees, the ants, all of them are arthropods. But only some of them are insects.
An insect’s has three parts, the head, the breast, and the belly.
The head is the sensor center. The main sensors of an insect are a pair of feelers, and eyes. Some insects have one or two pair of eyes; some others can have thousands of eyes. Another task of head is taking food.
Breast is driver center of an insect. All its three pairs of legs are growth on the breast.
Belly takes charge of breed and metabolism. Metabolism means to absorb food and excrete waste out of the body.
Now we know, a spider is not an insect, because it has four pairs of legs. But the butterflies, the bees, the ants, the dragonflies, and the mosquitoes are insects. Have you ever observed the caterpillars? Some of then have thousands of legs, some of them haven’t even one leg. But they are also insects. Why? Because all these characters are describe an imago, a matured insect. But the caterpillars are only larvae. They will metamorphosis into butterflies finally.
Do you know how many species of insects on the earth? Someone believes that that there are more than 10 millions species of insects on the earth. Let’s only consider the already discoed species. Suggests all the species of creatures on the earth were in one pie, on the other word, about 1 million species. Three fourth of the pie is occupied by the insects. And one third of the insects are beetles. One sixth of the insects are butterflies, one sixth is bees and ants, one sixth is flies and mosquitoes, and one sixth is other insects.
You may curious that why there are so many kinds of insects. I know some of the reasons.
First, in about hundreds of million years, insects are the only creatures on this earth that can fly until birds emerged. They can easily migrate to some other habitat, or avoid their enemies with help of their wings. Insects exploit every inch of plot once they come to the earth.
Second, the size of a single insect is usually tiny. The biggest insect is just like an egg-size. For smallest ones, 10 millions of them assumed tighter equals one egg. That means an insect only need very limited foods to be feed. For example, a cockroach can survive for two months without eating anything. And, they can hide themselves anywhere.
The third, almost everything can be the foods for insects. A cockroach can live in a television set all its live by eating the wax on the board.
Another reason is their incredible reproducing capability. In average, an insect can lay sounds of eggs each time. Some one can lay millions of eggs.
The last one is more unbelievable. The first insect appeared in 350 million years ago. In such a long period the insects already adapted this world perfectly. They evaluated various capabilities to protect themselves. Some of the capabilities are even hard to image. For examples, some insects can live in desert where’s temperature is higher than 50 Celsius degree. Some other insects can live in –50 Celsius degree. Some flies can live in pure salt or pure oil, even in pure CO2.