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any of more than 4,000 species of carnivorous, aquatic beetles (insect order Coleoptera) that prey on organisms ranging from other insects to fish larger than themselves. Diving beetles are oval and flat and range in length from 1.5 mm to more than 35 mm (0.06 to more than 1.4 inches). They are well adapted to an aquatic environment. The hind pair of legs is long, flattened, and fringed to provide surface area that aids in flotation and swimming. The spiracles (openings through which the beetle breathes) are on the abdomen just under the tips of the wing covers (elytra). When in a resting position, below the water surface on an incline with the head down, the beetle raises the tips of the elytra and breathes through the spiracles. When ready to dive, it stores a supply of air under its wings for breathing while under water. Diving beetles are so streamlined that the males of some species have sucker-like cups on the first pair of legs so that they can hold on to the smooth surface of the female during mating.