The bordered little diver.—In nearly every English pond there at times occurs a beetle—an inch or more in length—which is known to naturalists as Dytiscus marginalis. The name is somewhat cumbrous, but it would be difficult to find a more appropriate one; for “bordered little diver”—the plain English of the scientific term—indicates at once the peculiarities which soonest strike the observer: the creature’s skill in diving, and the yellow band which runs round the edge of the olive-green body. The outline of the beetle is an almost [Pg 359] unbroken oval, and it is worth noticing that either such a boat-shape (Fig. 224, B), or the cigar-shape of the torpedo is adopted by almost all actively swimming aquatic animals. The resistance of the water is further lessened by the smoothness of the beetle’s armour, which forms a hard shell enclosing the body. As in all insects, the body is divided into head, thorax, and abdomen. The eyes are large, and are so arranged that the animal can at the same time see objects both above and below—a great advantage to a creature living so active a life. The feelers are very sensitive organs of touch, and possibly of smell also. The jaws consist of one pair of mandibles and two pairs of maxillae, and are shaped much like those of the cockroach; they are powerful, and render Dytiscus a very formidable enemy to the more peaceable inhabitants of the pond. Fig. 224.—A beetle of the Dytiscus family. A, larva; B, adult insect (male).