Among those which live in the water there are several most interesting insects. There are the water-striders, for example, which you can see running about on the surface of any pond, and which look like narrow-bodied long-legged spiders. But you will notice that they only have six legs, whereas true spiders always have eight. They skim about on the water by means of the middle and hinder limbs, the front pair being used in catching prey. And when they have caught a victim they suck its juices through their sharp little beaks. Then there is the water-boatman, which always swims on its back. The reason why it does so is that when its body is in that position it is shaped just like a boat, while its long hind legs serve as a pair of oars. So the little insect really rows itself through the water. On a bright sunny day you may often see it resting on the surface of a pond, with its hind legs thrown forward in readiness for a stroke. And if even your shadow falls upon it, or it feels the vibration of a heavy footstep, it will dive down in a moment to some hiding-place among the weeds. If you ever catch a water-boatman, be careful how you handle it, or it will give your finger a very painful prick with its sharp beak. 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