This insect is found plentifully in all still waters during the summer months. Its larva is a soft elongate grub, provided with six slender thoracic legs, and a pair of powerful mandibles. The posterior extremity of the body is furnished with two curious appendages bearing a spiracle at the apex of each, which the larva frequently protrudes above the surface of the water. The air is taken in through the spiracles, and conveyed to all parts of the body by two main air-tubes, one of which springs from each spiracle, and branches throughout the insect in every direction. During the spring months the larvæ may be found of various sizes in similar situations to the imago; they are very voracious, devouring freshwater shrimps, _Ephemera_ larvæ, and occasionally, when pressed by hunger, they will even destroy individuals of their own species for food. These they capture by means of their powerful mandibles, retaining a firm hold of the victim until they have consumed all the fleshy portions, the rest of the carcase being thrown aside, and a fresh search made for more. One individual I kept for some time, remained perpetually concealed in a small patch of green weed, growing in the middle of its aquarium. In a short time it became surrounded with the skeletons of small water shrimps which had been seized by the larva as they passed by its hiding place, the unfortunate crustaceans only discovering their enemy when it was too late. I have not yet observed the pupa of this {23}insect, but it probably does not differ materially from those of its European allies. Although so very different in general appearance to the preceding insects, this beetle will be found on careful examination to agree with them in all important respects, being only what a ground beetle might naturally become if forced to lead an aquatic existence. Breathing is effected in all the water beetles by the spiracles of the abdomen, which alone are developed. The air is taken in between the elytra and the body, and owing to the convexity of the former, a supply can be retained sufficient to last the insect some twenty or thirty minutes. The beetles may be often observed with the extremity of their elytra protruded above the surface, renewing their supplies of air. On very hot days _C. rufimanus_ may be occasionally seen flying with great rapidity far away from its native ponds. When doing so it makes a loud humming noise, and is a much more conspicuous object than when in the water. Group CLAVICORNIA. Family NITIDULIDÆ. _Epuræa zealandica._