_Bembidium biguttatum_ may be identified by its brilliant bronze-green colour, and the two distinct impressions on the elytra which have suggested the specific name. _B. pallidipenne_ is, as its name implies, a pale-winged species, the elytra being of a light yellowish colour. _B. fumigatum_ is so called on account of the smoky tint of the elytra; and the last species of the same genus figured (_B. quadriguttatum_) may be known by the four conspicuous spots on the deep violet-coloured outer wings. The same family contains an interesting little beetle--_Cillenium laterale_--only about one-sixth of an inch in length, that lives among the refuse washed on the beach, where it feeds on the sandhoppers; and although the latter are so much superior in size, the beetle has no difficulty in holding and killing its prey, always seizing it on the ventral side of the body, which is less protected by the hardened skin. This species, which is of a copper colour, does not confine its ravages to that portion of the beach which is above high-water mark, but often allows itself to be covered by the advancing tide, remaining submerged for a considerable time. Another species--_Aëpus (Æpys) marinus_--is even more aquatic in its habits, for it searches out its prey among stones, chiefly at the mouths of rivers, below high-water level, and is often submerged for hours together. It is even provided with air-sacs to enable it to withstand such prolonged submersions. [Illustration: FIG. 224.--MARINE BEETLES 1. _Æpys marinus._ 2. _Micralymma brevipenne_] There is another section of beetles which has elytra so short that they cover only a small portion of the abdomen; but although so short, these elytra completely cover the long membranous wings, which are folded up beneath them in a wonderfully compact manner. The section referred to is termed _Brachelytra_, from the feature just mentioned, and includes a few species that are more or less marine in their habits. One of them--_Micralymma brevipenne_--lives under stones below high-water level, and apparently passes through all its stages within reach of the waves. Another of the _Brachelytra_ (_Bledius_) burrows into the sand or mud near high-water mark, throwing up the débris as it proceeds. Both these beetles are carnivorous, and the latter is in turn preyed upon by a ground beetle of the genus _Dyschirius_, which hunts and devours it within its own home. The reader will have observed that the sub-kingdom _Arthropoda_ is not only a very extensive one in the sense that it contains a vast number of animal forms, but also that its members exhibit a very great variety of form and structure; and the beginner will probably find no little difficulty in locating his specimens in their correct position in the scale of life. The following table, however, will serve to show the general classification of the group at a glance, and thus form a basis for a more detailed study at any future time:--