Belongs to: beetles

Great diving beetle Dytiscus marginalis

Also known as: great water beetle


Best time to see: Mar to end Aug

Key facts

The largest of the diving beetles found in Britain, occupying well-vegetated ponds and lakes

Diving beetles carry air down with them in a cavity in their body, and are strong swimmers and also strong flyers

Young and adults attack fishes and frogs as well as small invertebrates

Recognition

Rounded reddish-brown body with a yellow border, up to 35mm; powerful hind legs are fringed with hairs to aid swimming

The males have smooth wing cases and suction pads on their front legs; females' wing cases are ridged

Often fly at night to find new habitat, sometimes landing on glass rooves and wet roads by mistake

Lifecycle

Females lay their eggs in cavities that they cut into the stems of aquatic plants above the water line

The eggs hatch after several weeks into scorpion-like larvae with large jaws

Pupate and emerge as adults during the summer, and can live for several years

  • Main photo
  • female

Photo ©

Photo © Tony Gunton