notes

The family Haliplidae is remarkable for

the enlarged coxal plates of the adults,

covering the base of the hind legs. Adults

collect large air bubbles that they hold

under the elytra and coxal plates. It is

thought that adults of the genus Brychius,

which live in flowing water, can use this

air bubble like a gill, to enable them to

breathe under water for long periods

of time, therefore reducing the risk of

predation or of being caught by the current

Larvae of Haliplidae are aquatic and graze

almost entirely on algae, either filamentous algae

such as spirogyra, or stoneworts such as the genus

Chara. Adults eat small invertebrates and the adults

of one species, the European Haliplus lineolatus, are

thought to feed mainly or entirely on Hydrozoa,

small freshwater relatives of jellyfish and

sea anemones called Hydra – because their

nematocysts, or stinging cells, have been found

in the beetles’ gut contents.

left | Haliplus The characteristic narrow,

pointed larva of a European member of

this large genus, clinging to a water plant.

below | Brychius elevatus Inhabiting

fast-flowing water, this European beetle

is thought to have declined due to loss

of water quality.