Centipedes (members of the arthropodan class Chilopoda) are common and relatively familiar animals which are found in soil and litter or under stones or bark. They are soft-bodied and dorsoventrally flattened having from 15 to 181 pairs of legs, one pair to each trunk segment. Species from temperate regions are usually of moderate size, varying from 1 to 10 cm in length and of drab brownish or yellowish coloration. Many tropical species of the order Scolopendromorpha are large, one reaches a length of 26 cm, and are brightly coloured: red, black and orange, green or violet.

Like other arthropods, the centipedes are bilaterally symmetrical, metamerically segmented animals with a double ventral nerve cord, typically with a ganglion in each segment and concentrations of nervous tissue above and below the gut at the anterior end of the body. A circulatory system is present carrying blood forwards in a dorsal vessel and backwards in a ventral vessel. The body is covered by a non-living layer, the cuticle, which is secreted by the epidermis. The cuticle is in the form of relatively rigid sclerites separated by flexible arthrodial membranes; it is shed periodically to allow growth, a phenomenon known as moulting or ecdysis. The anterior part of the body is differentiated to form a head which bears a pair of antennae, a pair of jaws (mandibles) and two pairs of jointed legs modified to form mouthparts (the first and second maxillae).