There are over 12,000 described species of millipedes placed in 16 orders. On this website, the orders, their suborders and families are listed under Taxonomy and their possible relationships are illustrated in Millipede Systematics in the Tools & Resources section. The basic parts of a millipede body and the terms used to describe them are explained in the Introduction to Millipedes section.
The body of a millipede is divided into two distinct parts, the head and the trunk. The head is at the front of the animal, and is easy to identify because it houses the eyes, antennae and mouthparts. The main functions of the head are sensing the environment around the millipede using the eyes and antennae, and eating using the mouthparts. The eyes of the millipede are composed of ocelli, or simple eyes. There are usually multiple ocelli that compose an eye, but certain millipede orders lack eyes entirely. The trunk is composed of several body rings. The first body ring is called the collum and is found directly behind the head. The collum segment is legless. The next four body rings behind the collum each have only one pair of legs. All remaining body rings, except the very last few have two pairs of legs. The number of these apodous body rings, or rings that lack legs, can vary. Many millipedes have ozopores, or defense glands, on the sides of most of their body rings. The millipede produces a chemical defense that is exuded through the ozopores to deter predators or other curious animals.