The tracheal system consists of a single pair of stigmata on the under surface of the head, and the tracheae connected with them.
Order V. Pauropoda.
The Pauropoda, which form the fifth Order of Myriapods, are as yet very imperfectly known. Pauropus was discovered by Sir John Lubbock, and its discovery was announced by him in 1866. He found this little Centipede in his kitchen garden among some Thysanura, and at first considered it as a larval form, but continued observation showed that it was a mature creature. He described it as a small, white, bustling, intelligent little creature about 1⁄25 inch in length.
The antennae are very curious and highly characteristic of the Order. They resemble those of Crustacea rather than those of Myriapoda. Each antenna is composed in the following manner. First there is a shaft of four joints. From the fourth joint of this shaft spring two branches; one of these two branches is narrower than the other, and ends in a long thin bristle composed of a great number of joints. The other and broader branch bears two such bristles, and between them a small pear-shaped or globular body, the function of which is unknown.
The mouth parts consist of two minute pairs of appendages, the anterior pair toothed and the posterior pointed. The body is rather narrower in front; the segment behind the head has one pair of legs, the second, third, fourth, and fifth behind the head two each. The posterior legs are the longest; the genital organs open at the base of the second pair of legs, between these and the third pair. The manner of breathing is as yet unknown, tracheae not having been discovered.
Pauropus at first looks most like a Chilopod, but differs from that Order—
1. In the form of the antennae.
2. In the absence of poison claws and in the form of the mouth parts.
3. The opening of the generative organs being in the front part of the body.
It differs from Chilognatha in the following respects:—