Diving Beetle Dytiscus marginalis

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Diving beetle and their larvae are voracious aquatic predators. Larvae can tackle large prey such as tadpoles and small fish.

Size Up to 35mm in length.

Description

This is a large black beetle with yellow borders around the thorax and elytra (wing cases). The black parts of the beetle are iridescent and appear green in certain lighting conditions. Its long hind legs are flattened and fringed with thick hairs which it uses to propel itself through the water. The female is larger than the male and has a series of grooves along her elytra. Males have suction pads on their front legs that are used for gripping onto the female during mating.

Distribution

Common all over Europe.

Habitat

Found in ponds and still water with plenty of vegetation.

Diet

Both adult and larvae are voracious aquatic predators but the larvae usually tackle larger prey such as tadpoles and very small fish. The jaws of the larvae are hollow and are used to suck juices from their prey.

Behaviour

Although an aquatic beetle it can still fly and in spring and autumn will fly at night in search of new ponds. They are often confused by man-made structures such as greenhouses which, to their eyesight, look like ponds. It is difficult for them to get airborne from a flat surface such as the roof of a greenhouse, and many dry out and die in the sun the next morning.

Neither the adult nor the larvae have gills and both have to regularly visit the surface of the water for air. The adult stores air in a small chamber under its elytra.

Reproduction

Femaleslay eggs in the stems of water plants. She cuts small slits into the plant stems and lays one egg in each. Larvae pupate in damp soil near water. Newly emerging beetels are white, but as it hardens it develops the normal dark colouration.

Conservation status

They are not listed as endangered on IUCN Red List.