BEETLES ~ Order Coleoptera.

Adult aquatic beetles are air-breathing. The dytiscid pictured here is obtaining air through the posterior tip of its abdomen, seen just breaking the surface as the animal hangs head down in the water. The hind legs are adapted for swimming, being more or less flattened and heavily fringed with hairs. Adult beetles are characterized by the front pair of wings hardened as elytra that cover and protect both the hind pair of wings and the abdomen. Beetles are most typically found in ponds of various sizes. Adult aquatic beetles are capable of flying (the elytra open sufficiently for the wings to unfold and beat) and distribute to isolated bodies of water by this means.

When completed, the following key will cover both adult and immature stages, both of which are usually aquatic. The larvae somewhat resemble very small damselfly nymphs, although minimal taxonomic data on the immature stages of the Hawaiian species exists.