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Great diving beetle

Great diving beetle

The great diving beetle dytiscus marginalis is one of our largest water beetles, although there are several closely related species.

This versatile and common beetle is found in still or slow flowing waters, occasionally fast flowing. Most likely in small ponds, adults can be found all year round but peaks are usually in May and September.

The larvae are carnivorous, feeding on a wide range of aquatic life; they are ferocious hunters. When ready to pupate, they crawl out of the water to look for a suitable site in damp soil, perhaps several metres from the pond. Adults hatch around September and overwinter at the bottom of the pool until spring, when they look for a mate and lay eggs. Adults can live for several years in captivity. Like the larvae, they are carnivorous; they tear their prey into pieces and swallow them. They take off and fly vertically at night and are therefore able to colonise other areas.

great diving beetle dytiscu

The Balfour-Brown Club (Aquatic Coleoptera Conservation Trust) was formed in 1976 to study water beetles.

Photos: Paul D. Brock

ID Tip

ID Tip

26-32 mm long, black with a continuous yellow margin around the thorax and wingcases. The underside is yellow. Try a pond-dipping event in the area sometime e.g. Blashford Lakes, and this is one of the likely finds.

Lead Ranger


'To help ground nesting birds rear their young safely, keep yourself, dogs and ridden horses on the main tracks from the beginning of March to the end of August.'

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