Other Common Names
Predacious Diving Beetle (applies to family)
larvae known as water tigers (applies to family)
Numbers
Nearctica.com lists 11 species. All species except
habilis occur in Canada.
26 species worldwide
Identification
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.
Range
throughout North America, including the arctic
also represented in Eurasia
Habitat
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
Season
varies by species but adult flight season ranges from March to November
Food
larvae and adults predaceous on fish larvae, mosquito larvae, other aquatic invertebrates, and sometimes tadpoles and salamanders
Life Cycle
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)
Remarks
Author of genus is Linnaeus, 1758.
See Also
Hydrophilus, a Giant Water Scavenger Beetle
Print References
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)Internet References
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)
Contributed by
Cotinis on 7 April, 2005 - 10:31pm
Additional contributions by
Robin McLeodLast updated 17 May, 2007 - 2:04am
