6. Scolopendrella has twelve pairs of legs, and Campodea, like all Insects, has only three.
I will now go on to an account of their anatomy. The body is small and slender, and is covered with a delicate shell or exoskeleton of chitin, which is so thin as to be almost transparent.
The antennae are long, and are composed of many joints of equal size.
The mouth parts consist of—
1. An upper lip.
2. A pair of mandibles.
3. A pair of maxillae.
The segments are not all of equal size. Some are larger than others. The larger and smaller segments are arranged alternately, and the smaller do not bear legs. As before stated, there are twelve leg-bearing segments.
At the end of the body there are two hook-like appendages which are pierced by a canal, through which is poured the secretion of a pair of glands. Near the sides of these appendages are a pair of sense organs, consisting of long hairs connected with nerves.
The digestive canal is a long straight tube passing through the length of the body. In the middle it is much enlarged, so as to form a stomach with a glandular coat. Posterior to the stomach the digestive tube receives the contents of two Malpighian tubes which act as kidneys.