Genus Cybister

Author of genus is Curtis, 1827. From Greek cybister, a diver. (Based on Internet searches.)

Nearctica.com lists five species.

This genus is more diverse in the tropics

Circa 26-33 mm for North American species

Large water beetles. In southeastern United States, the only large (25-35 mm) members of this family are Cybister and Dytiscus. Hind legs broad. Metatarsal claws unequal, inner one smaller, sometimes absent. Metatarsi have fringe on outer margin, lacking in Dytiscus. Male has modified protarsus, used for grasping female during mating. Structure differs in Dytiscus. Male Cybister has, apparently, two rows of punctures on each elytra, apparently lacking in Dytiscus. White, fig. 33 illustrates both these characters well. (1)

Larvae are very large (up to about 8 cm), have no cerci, and have a "tooth" at the anterior region of the head.

Found mainly in the southern regions of the US with Cybister fimbriolatus the only species of the genus reaching Canada; the range of this genus is considered complementary to that of Dytiscus, the latter being more common and diverse in northen latitudes (2).

In the deeper, more open portions of ponds and lakes; readily attracted to lights at night

Carnivorous

Members of this genus and Dytiscus are regularly utilized as food in parts of Asia and elsewhere. For example, see here for a list of commonly used food species in East Asia.

Dillon, pp. 153-154, Plate XVI (3)

Ciegler, p. 88, fig. 5.102 describes and illustrates C. fimbriolatus. (4)

Larson DJ, Y. Alarie, and RE Roughley. 2000. Predaceous Diving Beetles (Coleoptera: Dysticidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska. pp. 830-833. Describes diagnostic characters and biology of the genus; includes a key to all 5 North American species and a more detailed description of C. fimbriolatus, the only Cybister species that reaches Canada

White, fig. 33, has illustration of male tarsus, comparing with Dytiscus. (1)

North Carolina State University lists C. fimbriolatus from that state.