Life in Ponds and Streams.
The last order of insects calling for notice here is the Coleoptera or sheath-winged insects, popularly known as beetles, and characterised by the hard and horny nature of the front pair of wings (elytra), which are modified into sheaths and serve to protect the second pair; the latter are thin and membranous, usually adapted for flight, and lie folded beneath the former when not in use.
One large section of beetles is known as the Geodephaga or Ground Beetles—a group of very predaceous insects that burrow into the soil and attack almost every living thing that comes in their way, and well represented by numerous species that may be found in our gardens, and, in fact, almost everywhere.
A considerable number of these insects show a decided preference for salt marshes and the sea shore, where they hide under stones, or burrow into the sand or mud in search of their prey. They are not marine in the strictest sense of the word, for they are not adapted for a life of submersion in water, either in the larval or in the perfect condition; yet they are often found below high-water level, and some species burrow into the sand of the beach as the tide advances, allowing the water to cover them for hours together.
One interesting family of the ground beetles (the Bembidiidæ) includes several small species, all of which frequent salt and wet places, such as salt marshes, the mouths of rivers, and the sea shore. We give enlarged illustrations of a few of these, the actual size being denoted at the side of each.
Fig. 223.—Marine Beetles of the genus Bembidium
1. B. biguttatum. 2. B. pallidipenne. 3. B. fumigatum. 4. B. quadriguttatum