Centipede, a general name for the members of one of the orders of the class Myriapoda. Popularly they are sometimes called Galley-worms, technically Chilopoda. Like the Millipedes, which form the most important neighbour order, the Centipedes are segmented animals bearing jointed appendages, having a well-defined head furnished with feelers and jaws, and breathing by means of air-tubes or tracheæ.
Structure.—The Centipede is like a primitive insect in its general structure.—(a) Externals.—The body is divided into well-marked rings, but the region behind the distinct head is practically uniform, and not divisible into thorax and abdomen. Just behind the head a few rings appear to be fused. The number of rings varies from twelve to more than twelve times as many. In counting the rings the ventral surface should be looked to, for the dorsal shields often overlap. The rings are flattened from above downwards, and each bears a pair of appendages. Dorsally and ventrally the skin is hard and horny. Glands occur in various positions. (b) Appendages.—The head, which is covered by a flat shield above, bears (1) a pair of antennæ, usually of considerable length, and consisting of from twelve to over one hundred joints; (2) a pair of small, strong, toothed, and bristly mandibles; (3) a pair of under-jaws, usually with palps. The next appendages are limb-like, and are followed by a modified pair of legs, the basal pieces of which generally meet in the middle line, while the strong joints terminate in a sharp claw, at which a poison-gland opens. These appendages are obviously of use for seizing and killing the prey. The legs of the other segments are usually seven-jointed, sometimes bear spurs and glands, and are generally clawed. The last pair differ in size and form from the rest, and are turned backwards. (c) Internal Anatomy.—The large brain is connected as usual with a ventral chain of ganglia. Compound eyes occur in one family, simple eyes in many, while the feelers, certain bristles, and portions of the skin are also sensory. In some cases there is a special well-defined sense-organ of undecided function in front of the head, or on one of the jaws. The alimentary canal is straight, and has associated with it salivary and digestive glands, and excretory (Malpighian) tubules. The heart is represented by a chambered dorsal vessel. Tracheæ or air-tubes open on the sides of the body, sometimes on each ring, often on alternate segments, ramify throughout the tissues, and are connected together on each side by a longitudinal stem. The reproductive organs are usually tubular, and open on the last ring of the body. A distinct penis is sometimes present.
Life and Habit.—Centipedes are darkness-loving animals, nocturnal in their food-hunting, lurking under stones or among rotten wood and the like during the day. Their powers of vision are very poorly developed, and most of the sensory work is tactile. Only in one family (Scutigeridæ) are there compound eyes, in most forms only simple eyes, in many none at all. The recent researches of Plateau and others have shown that these creatures can distinguish light from darkness, but do not need eyes to do this; species with eyes do not apparently get on much better than those without them; those with eyes seem to perceive bright objects reflecting much white light, and in some cases conspicuous movements, but probably in no case the forms of objects. Moving actively about at nights, feeling their way by means of their antennæ, which function as a blind man's staff, they light upon insects, worms, and other small animals, which they seize and kill with their poison-bearing appendages. They are all voracious carnivorous forms, not vegetarian like the Millipedes. Some forms can run with some rapidity, and wriggle about in curious serpent-like fashion.