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Great diving beetle

Dytiscus marginalis

A big, glossy beetle and a fierce underwater hunter, with a bright yellow edge.

Size
About 3cm long
Look for it
March to October
Where
Weedy ponds and lakes

My spotter's list

Swims fast, dives out of sight and pops up somewhere else. Move your pointer and see.

When to look

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Diving beetle

Good to know

Six things about the diving beetle

Air

A built-in air tank

It carries a bubble of air under its wing cases to breathe underwater, and comes up tail-first to refill it.

Hunting

A fierce hunter

Great diving beetles catch tadpoles, insects and even small fish.

Larvae

Water tigers

The larvae are even fiercer hunters than the adults, with huge curved jaws. They're nicknamed water tigers.

Flying

Night flights

They fly at night to find new ponds, and sometimes land on shiny car roofs or greenhouses by mistake.

Legs

Paddles

Their flattened, hairy back legs work like oars, pushing them fast through the water.

Edges

Look for the yellow

The yellow edge round its dark green-brown body is the easiest way to recognise it.

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
Out and about

How to spot one

Watch a weedy pond for a large dark beetle coming up tail-first for air, then rowing back down with its back legs.

Lend a hand

How to help

A pond with plenty of plants and no fish gives them prey and cover. They fly in on their own once a pond is ready.

Keep going

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