Great Silver Beetle

Great Silver Beetle

Great Silver Beetle - Hydrous piceus

This is the largest water beetle in Italy and one of the largest European Beetles, reaching as much as 50 mm in length.

The black coloured adult, with a greenish reflection is vegetarian, feeding mainly on decaying plants. Although its 2nd and 3rd pairs of legs have swimming hairs, it is not a good swimmer and spends most of the time crawling along water plants. The ventral side of its body bears a spine which can inflict a painful wound.

The Silver beetle has a peculiar method of replenishing its dorsal air reserve, a bubble kept under the elytra, and ventral air supply, trapped by a series of water-repellent hairs which gives the animal its characteristic silver look.

In fact, whilst the other water beetles use the tips of their abdomens, the Great Silver Beetle uses its hairy, clubbed antennae.

When the antennae reach the water surface, the water-repellent hairs make a continuous channel of air which runs from the antennae to the abdomen and finally reaches the stigma connected to the dorsal and ventral air reserves.

The adults mate in late spring and the female lays fifty or so eggs in a typical silken sack that either floats freely on the water surface or is anchored to some water plants. The larvae are carnivorous and breathe through abdominal spiracules.

Once common in stagnant waters rich in vegetation, it is now rather rare as it is taken by collectors, and because of the disappearance of its natural habitat.