Genus Dytiscus

Predacious Diving Beetle (applies to family)

larvae known as water tigers (applies to family)

dye-TISS-cuss

Nearctica.com lists 11 species. All species except habilis occur in Canada.

26 species worldwide

adult length 22-40 mm

larva length to 60 mm

Large, elongated/oval aquatic beetles. Dorsal surface mostly brown to black, sometimes green. Pronotum with or without pale borders. Elytra usually bordered with yellow. Pronotum and/or elytra of female variably smooth or grooved. Metatibiae much longer than broad, outer apical spur very thin. Protarsi of male have two large disks (and small disks) used to grasp female during mating. Hind legs move synchronously while swimming; adults often attracted to light.

Larvae are up to 6 cm, with prominent cerci and dense lateral fringes of hair on the last 2 abdominal segments and cerci. The anterior portion of the head is rounded.

throughout North America, including the arctic.

also represented in Eurasia

permanent or temporary freshwater ponds and pools (D. marginicollis may occur in saline ponds), plus streams and rivers; usually found on or among aquatic plants

varies by species but adult flight season ranges from March to November

larvae and adults predaceous on fish larvae, mosquito larvae, other aquatic invertebrates, and sometimes tadpoles and salamanders

one generation per year; mating occurs in late fall and/or early spring; eggs injected singly into underwater plant stems; fully-grown larvae creep out of water and pupate in moist earth, then emerge as adults in about a week and return to water; overwinters as an adult in permanent waters (D. hybridus may overwinter on land)

Author of genus is Linnaeus, 1758.

Dillon, pp. 148-149, plate XV--describes, illustrates four species. (1)

Ciegler, pp. 83-84, fig. 5.92 describes two species. Fig. 5.2 illustrates disks on male tarsus. (2)

White, fig. 33, has illustration of genus, including male tarsus, comparing with Cybister. (3)

Papp, p. 182, figs. 181-183 (4)

Arnett and Jacques, p. 113, fig. 288 (5)

live larva and adult images of undetermined species (U. of Michigan)

pinned adult images of 9 of the 11 North American species [page one of two], plus links to description, distribution, biology, etc. (U. of Alberta)

distinguishing characteristics of several species (enature.com)