A Great silver water beetle, Hydrophilus piceus.
Like other silver water beetles, Hydrophilus piceus, is so-called because, when submerged, its underside appears silver because of the layer of air held by a covering of small hairs. It swims with alternating leg movements - the ends of their middle and hind legs being lined by a fringe of hairs. These beetles may be found in areas of still, muddy water where they scavenge on plant material and detritus, but also worms and water snails. The adults, which can reach 5cm in length, are also strong fliers and may be encountered some distance from bodies of water.
Their larvae are predators of freshwater snails (they drill holes into their shells to feed on the soft flesh), small invertebrates, tadpoles, and tiny fish.
