Great Diving Beetle

Dytiscus marginalis belongs to Dytiscidae, the predaceous diving-beetle family. [5]

The oval body is dark brown to black above, edged with yellow, and yellow beneath. Males have enlarged adhesive pads on the front legs. Grooved female wing covers are conspicuous, but smooth females also occur: a Japanese study confirmed both forms in D. marginalis czerskii. [2][3][4]

The species is recorded in British freshwater habitats, including the New Forest. It occupies ponds and slow-moving water, where its flattened, streamlined body and swimming legs suit submerged movement. [3][2]

Adults hunt aquatic insects, tadpoles and small fish. Larvae have prominent curved jaws and take tadpoles and other insects; they can also prey on one another. [2]

Adults replenish the air held beneath the wing covers by raising the abdominal tip to the surface. They can leave the water and fly between ponds. [2]

In the Japanese female-morph study, a male descended from a smooth-winged mother had the same examined mitochondrial COI sequence as a known grooved female. The result supported two female forms within the studied subspecies. [4]

Linnaeus described Dytiscus marginalis in 1758. [1][5]

The underside reveals the yellow body, broad swimming legs and, in males, the foreleg attachment pads. A smooth dorsal surface alone does not establish sex. [2][3][4]

Keep the enclosure closed and display it in indirect light, away from heat and damp conditions. Handle the frame by its edges and clean only its exterior according to the maker’s instructions.