of a telescope, and can readily be moved in any direction. Such a confirmation is well exemplified by the Staphylinidæ, which elevate and twist about their abdomen with the utmost facility, and even turn it over the back to push the wings under their short cases.[1] The whole of the segments are lined internally with a soft membrane, which connects them, and retains them in their places, without impeding their movements. This membrane becomes visible when the abdomen is in a distended state, as in a gravid female, when the abdomen seems to form a bag, with horny plates arranged in a certain order over its surface.
An opening for the respiratory organs, which ramify through the body, may be observed near the lateral margin of each segment. These openings are surrounded with a hard ring, and are called spiracles or air-holes, (Stigma, Spiracula.)
It has been well observed that each of the three great divisions of the body is the appointed seat of a separate set of organs, all of them alike important in the animal economy. As the head contains the organs of mastication, and the thorax those of motion, so the abdomen is the appropriate site of the generative organs. These, however, are chiefly internal, and will be most conveniently considered when treating of the anatomy of the abdomen. Such external appendages, too, as are more or less accessory to the organs alluded to, as well as various others which, as far as known, have no connection with
- ↑ See Lacord. Introd. I. 447.
