No larva or other animal that is of any value should be kept in the same aquarium with the Water Scorpion. Dr. Hill, who annotated the English edition of Swammerdam, says, ‘There is not perhaps in all the animal creation so outrageous or fierce a creature against those weaker than itself as the Water Scorpion. It destroys, like the wolf among sheep, twenty times as many as its hunger requires.’ The Rev. G. C. Bateman placed one in a saucer with a tiny minnow; ‘but no sooner did the little fish swim within reach of the fore-legs of the scorpion than it was seized by them, and pressed against the hungry creature’s rostrum.’ It seems to be particularly fond of Asellus, the water woodlouse. I have often taken dead specimens of this crustacean, sucked completely dry, from between the raptorial legs of the insect. One specimen was so thoroughly cleaned out that it was mounted just as it was, the only preparation being a brief soaking in spirit. In examining the head the eyes may be readily distinguished, and on pressing the rostrum or beak with a needle, the proboscis will be forced out, just as one may force out the sting by pressing the abdomen of a bee or a wasp. In this group the antennae are three-jointed and concealed. When one begins to look for these organs he will probably come to the conclusion that the concealment is highly effectual. A very simple method of finding them in a spirit specimen is to take the insect between the thumb and index finger of the left hand, holding it up to the light in such fashion as to keep the first pair of legs well clear of the head. Then, with a needle held in the right hand, raise the thorax till it lies in the same plane as the body. Each antenna lies in a groove beneath the eye. Gentle manipulation with the needle will lift them out, so that they may be clearly seen, not only with the hand magnifier, but with the unassisted eye. Or the insect may be pinned down under water instead of being held in the hand, and the antennae lifted or brushed out of the groove. It will greatly simplify matters if, before attempting to raise the wings, the fact is borne in mind that the tip of the right wing-case lies over that of the left. It is perhaps as well to remove the wing-case altogether by inserting a needle under it, and gently raising it, using a little pressure in an outward direction. It will then be quite time to raise the wing and to see the method of folding and unfolding. [Illustration: FIG. 44.--Raptorial leg of Water Scorpion.] In Fig. 44 we have a representation of the raptorial (front) leg of this insect. This leg should be compared with the legs of other Insects--not in pictures only, but in actual specimens--that we may see how, while the general plan is preserved, different joints are modified to suit the special function of this limb--that of taking prey. (See also Fig. 43.)