Pond and stream · Beetles

Great diving beetle

Dytiscus marginalis

A large, oval, olive-black beetle edged in yellow, with long hairy back legs that it uses as oars.

Size: About 3cm long
Look for it: March to October
Where: Weedy ponds, lakes and ditches throughout Britain

My spotter's list

Swims after you, diving and bobbing up. Move your pointer and see.

When to look

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Diving beetle

Good to know

Six things about the diving beetle

Air

It carries its own air

It comes up tail first and tucks a bubble of air under its wing cases, like a diver's tank.

Hunter

A fierce hunter

It catches tadpoles, newts and even small fish.

Young

The water tiger

The larva has curved, hollow jaws and is even fiercer than the adult.

Fly

It flies at night

On warm nights it takes off to look for new ponds, finding water by the moonlight shining off it.

Mistake

Fooled by glass

It sometimes lands on greenhouses and wet roads, which shine like water.

Feet

Suckers on his feet

The male has sucker pads on his front legs, for holding on to the smooth back of the female.

The real thing

Photos of the diving beetle

Great diving beetle, photo 1 — Photo: Bernard DUPONT from FRANCE, CC BY-SA 2.0, Wikimedia Commons

Great diving beetle, photo 2 — Photo: Каїра Федір, CC BY 4.0, Wikimedia Commons

Great diving beetle, photo 3 — Photo: Thintkk, CC BY-SA 4.0, Wikimedia Commons

Photos are from Wikimedia Commons, used under the free licences shown. They have been resized, and cropped where they appear in link previews.

Out and about

How to spot one

Watch a weedy pond for a big beetle rising to the surface tail first, hanging there for a moment, then rowing back down. Take an adult with you.

Lend a hand

How to help

It needs plenty of underwater weed to hunt and hide in. Do not clear a pond out completely.

Keep going

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