Family 12, Gerridæ.—This family includes some very familiar insects, which may be seen running over the surface of every piece of water. These insects, of which several species are abundant in Britain, have boat-shaped bodies. The typical form is Gerris lacustris, which may be met with almost anywhere. They are predaceous in their habits, feeding upon other insects. Some nearly allied, but mostly very small species, with legs even longer in proportion than those of our common forms, are met with at sea within the tropics, and often at a great distance from land.
Fig. 92.—Galgulus Oculatus (Mag.)
Family 13, Galgulidæ.—This family only includes a few American species, which are generally brown spotted with yellow. Galgulus oculatus inhabits the southern part of the United States, and measures about two-fifths of an inch in length.
Family 14, Nepidæ.—The species of this family are not very numerous, but are of considerable interest. They are of large size, and very fierce and voracious. The genus Betostoma, found in the East Indies and America, includes the largest species of Heteroptera, some of which measure four and a half inches in length, and nearly six inches in expanse of the wing. Their food consists of small fish, frogs, etc.
Fig. 93.—Nepa Cinerea.
The best-known species in our own country is the Water Scorpion (Nepa cinerea), which has the power of inflicting a very painful wound if handled. It measures about an inch in length. In colour it is yellowish-grey, the back of the abdomen being red, and its large front legs, which somewhat resemble the claws of a scorpion, have given rise to the name by which it is popularly known. It is very common in stagnant water.
