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Close up on the head and thorax of a king diving beetle, a large black beetle with yellowish edges to the body

King diving beetle © Henry Stanier

King diving beetle

Britain's largest 'diving beetle' is an impressive creature, though it's not easy to find.

Scientific name

Dytiscus dimidiatus

When to see

All year

Species information

Statistics

Length: up to 3.8cm
Near Threatened

Habitats

About

The king diving beetle is a fitting name for this enormous aquatic insect, which has golden edges to its black body. It is the largest 'diving beetle' in Britain, reaching a length of 3.8cm. Diving beetles belong to the family Dytiscidae. They are streamlined beetles suited to swimming and are predators of other aquatic creatures.

In Britain, king diving beetles are fenland specialists, found in lowland drains, ditches and ponds. They seem to have a preference for partially shaded ditches. They are fairly rare beetles, found only in a few areas of England and Wales.

How to identify

A large aquatic beetle, with a domed back and rounded underside. It is black with gold trim on the sides of the pronotum (the section behind the head) and the sides of the wing cases. Its large size helps sets it apart from other diving beetles.

Distribution

Found in clusters in England and Wales, particularly around the Somerset Levels, the Gwent Levels, the Cambridgeshire Fens, Broadland and the coastal fens of Kent and Sussex.

Did you know?

Not much is known about the diet of king diving beetles in the wild, but laboratory studies have found that their larvae aren't too picky about what creatures they eat. They hunted small fish, water boatmen and even cannibalised other king diving beetle larvae. They seem to be mostly ambush predators. They sit still, waiting for prey to pass within a few centimetres, then pounce.