notes

Some species are indicators of water

quality. The largest European species,

the 2-in (5-cm) Great Silver Water Beetle

Hydrophilus piceus, disappeared from

much of its range during the twentieth

century, but is recently beginning to make

a recovery in some places as pollution with

agrochemicals is reduced

above | Hydrochara caraboides

The European Lesser Silver Water

Beetle is a typical hydrophilid,

showing the air bubble carried under

the body, and the enlarged palps.

below | Sphaeridium scarabaeoides

A dung-feeding water beetle

common in wet cowpats in much

of Europe and North America.

and by the palps of their mouthparts, which in

hydrophilids are long, usually longer than the

antennae, and are used to break the surface tension

of the water when collecting air.

A quite remarkable ecological feature of

Hydrophilidae is that a large proportion of species

have secondarily returned to life on land. The

majority of the subfamily Sphaeridiinae live in

wet compost, decaying seaweed, animal dung,

and other moist, nutrient-rich substrates. A few

members of the genus Helophorus have completely

escaped water and wet substrates, and larvae and

adults live entirely on dry land.