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524 illustration

Great diving beetle

Dytiscus marginalis

At between 30 and 38 millimetres, this is a relatively large beetle, whose streamlined body is well adapted for swimming, especially with its hairy hind legs that work as oars. It is dark, with yellow margins on the back and wing cases. The male’s wing cases are shiny, and the female’s furrowed. The larvae grow up to 60 millimetres long and have pointed jaws.

The diving beetle is common in freshwater wetlands that are rich in vegetation and can be found throughout Europe and America.

Thanks to the air supply under its wing cases, the beetle can stay underwater for quite long periods. The air supply is renewed at regular intervals at the water’s surface. Females lay eggs inside the stems of underwater plants. The larvae live in the water, coming to the surface to breathe. The beetles inject their prey with enzymes, sucking up the digested contents through their strong jaws. They eat tadpoles, snails, smaller insects (and even each other), and are also capable of killing small fish. Because of their hunting ability they are also known as “water tigers”.

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