The water-scorpion, too, is very curious. It is a flat, oval insect, of a dirty-brown color, which looks very much like a piece of dead leaf. It seems to know this quite well, for when it is hungry it always hides among dead leaves down at the bottom of the water, and keeps perfectly still. Then the other insects do not notice it, and as soon as one of them comes within reach it seizes it with its great jaw-like front legs, and plunges its beak into its body.
This insect is called the water-scorpion because it has a long spike at the end of its body, which looks something like a scorpion's sting. It is really a breathing-tube, however, the top of which is poked just above the surface of the water while the insect is lying at the bottom, so as to enable it to breathe quite easily.
Aphaniptera
The order of the Aphaniptera, or unseen-winged insects, is a very small one, consisting only of the fleas. The name has been given to them because their wings are so tiny that, even with the microscope, they can hardly be seen at all.
There are a good many different kinds of fleas, all of which suck the blood of animals through their sharp little beaks. Some of them are able to leap to a really wonderful distance, by means of their powerful hind legs. And they are so wonderfully strong that if a man were equally powerful, in proportion to his greater size, he would easily be able to drag a wagon which a pair of cart-horses could scarcely move!
Diptera
The last order of insects is that of the Diptera, or two-winged flies, which seem to have two wings only instead of four. But if you look at them closely, you will see a pair of little knob-like organs just where the hind wings ought to be. And these little organs, which we call balancers, are really the hind wings in a very much altered form.
Although they are so tiny, and look so useless, these balancers are used in some way during flight; for if they are damaged or lost the insect can no longer balance itself or direct its course in the air.
The Mosquito
The mosquito is a troublesome insect which most of us know only too well; for there are very few of us who have not suffered from the wounds caused by its beak. Its life-history is very interesting. The eggs, which are shaped just like tiny skittles, are laid in the water, and the mother gnat fastens them cleverly together in such a way that they form a little boat, which floats on the surface. After a time a little door opens at the bottom of each egg, and a tiny grub tumbles out into the water. It is a very odd-looking little creature, with a very small head, a very big thorax, and a very long tail; and it mostly floats in the water with its head downward, and the tip of its tail resting just above the surface.