The position of the cockroach in the insect class.—The cockroach is familiarly known as the “black-beetle,” but the name is a very misleading one, because the true beetles differ from cockroaches not only in structure, but also in life history. Cockroaches are grouped with earwigs, grasshoppers, crickets, and locusts in the order Orthoptera,[28] a term alluding to the fanlike folding of the hind-wings. 63. A WATER BEETLE.[29] 1. The habits of Dytiscus.—Search a pond for water beetles. Put them in a wide-mouthed bottle with some of the weeds to be found in the pond, and take them home and observe their habits. Among the larger beetles—especially from ponds with a clear surface (not covered with [Pg 358] duckweed, etc.)—will probably be seen some with a yellow band round the edge of the upper surface. These are Dytisci. Notice the ovoid, smooth body, the breadth of the hind legs, and—in the male—the cup on each fore leg. Try to see how the legs of each pair are used. On what does the animal feed? Take a small piece of meat in a pair of forceps and hold it near the beetle’s head. If the animal does not notice it, stroke one of the feelers with the meat; how does the beetle behave? What is the use of the feelers? Notice how the beetle rises to the surface immediately it stops paddling. Which end of the body sticks out of the water? Why does the beetle need to come to the surface? In April look for larvae (Fig. 224, A), and describe their appearance and habits. 2. External characters.—Kill a Dytiscus by dropping it for a moment into boiling water. Examine it first from the dorsal surface, noting the almost unbroken oval outline, and the firmness of the armour. Notice that the inner edges of the two wing-covers fit closely together in the middle line. How does the beetle compare in this respect with the cockroach? Observe the small triangular plate between the anterior ends of the wing-covers; open out the covers and wings to find of which segment of the thorax it is a part. Examine the wing-covers and wings closely; notice that the wings are folded transversely as well as longitudinally. Spread and pin out one wing-cover and wing of one side, and draw a dorsal view of the animal. Dissect out the jaws and compare them with the jaws of the cockroach (Fig. 222). Examine and draw one leg of each pair.