Other Common Names
Predacious Diving Beetles (spelling)
Numbers
White, p. 97, lists 41 genera, 476 species
(1)
Classification of Nearctic Dysticidae (Adapted from Larson et al. 2000)
*Guide pages for tribes are not included in the guide at this time*
Subfamily Copelatinae Van den Branden 1885
Agaporomorphus Zimmerman 1921
Subfamily Hydrotrupinae Roughley
Hydrotrupes Sharp 1882
Subfamily Agabetinae Van Der Branden 1885
Agabetes Crotch 1873
Laccodytes Regimbart 1895
Tribe Methlini Van Der Branden 1885
Tribe Hydrovatini Sharp 1837
Hydrovatus Motschulsky 1853
Tribe Bidessini Sharp 1882
Comaldessus Spangler and Barr 1995
Brachyvatus Zimmerman 1919
Andocheilus Babington 1841
Bidessonotus Regimbart 1895
Crinodessus Miller 1997
Tribe Laccornini Wolfe and Roughley 1990
Tribe Hyphydrini Sharp 1882
Desmopachria Babington 1841
Pachydrus Sharp 1882
Tribe Hydroporinae Erichson 1837
Haedeoporus Young and Longley 1976
Stygoporus Larson and LarBonte 1994
Hydroporus Clairville 1806
Sanfilippodytes Franciscolo 1979
Hydrocolus Roughley & Larson 2000
Lioporeus Guignot 1950
Nebrioporus Regimbart 1906
Stictotarsus Zimmerman 1837
Tribe Matini Van Der Branden 1885
Tribe Coptotomini Van der Branden 1885
Tribe Agabini Thomson 1867
Agabinus Crotch 1873
Tribe Colymbetini Erichson 1837
Colymbetes Clairville 1806
Neoscutopterus Balfour-Browne 1943
Hoperius Fall 1927
Tribe Dytiscini Leach 1817
Tribe Acilini Thomson 1867
Tribe Hydaticini Sharp 1882
Tribe Cybistrini Sharp 1882
Megadytes Sharp 1882
Tribe Eretini Crotch 1873
Identification
Aquatic beetles whose hind tibiae have long hairs, other modifications for swimming. Dytiscids move their legs together like oars, in the manner of Backswimmers in the Hemiptera. In other aquatic beetle families, such as the Hydrophilidae, the legs are moved alternately.
(2)
In much of the eastern United States, the only two very large (25-35 mm) members of this family are
Dytiscus and
Cybister. They are similar, but several characters can be used to separate them.
(3) (4)
- Lower/outer hind tibial spur much wider than upper/inner in Cybister, spurs similar in size in Dytiscus.
- Metatibia of Cybister is short and broad, that of Dytiscus is longer and narrower.
- Prosternum of Cybister is greenish, that of Dytiscus is reddish.
- Structure of adhesive pads on male protarsi differs between the two genera. Dytiscus has two larger circular disks on with adjacent smaller ones. Cybister has a longer, broader pad. This is shown nicely in figure 33 of White. (1)
- On metatarsi, outer margin of Cybister has a narrow fringe, lacking in Dytiscus.
- Females of Cybister have long lengthwise scratches on elytra, lacking deep furrows found on some female Dytiscus.
- Male Dytiscus tends to have prominent rows of punctures on elytra, weak in Cybister.
Print References
Papp, pp. 60-62, discusses locomotion, has good discussion of family characters, including those of larvae
(2).
Ciegler, pp. 41-89, extensive keys
(4)
America Beetles, Vol. 1, Chapter 12
(5)
Castner, pp. 112-113, has representative photos, comparing with other aquatics.
(6)
Arnett et al. pp. 108-114
(7)
D.J. Larson, Y. Alarie, and R.E. Roughley,
Predaceous Diving Beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska(8) keys to all species, with descriptions and distribution maps for those found in Canada (which covers many also found in the lower 48 US)
Internet References
preserved adult images of 46 species with descriptions, distribution, habitat, and biology of each (Charles Staines, Discover Life in America, dlia.org)
Identification manual for the water beetles of Florida (Coleoptera: Dryopidae, Dytiscidae, Elmidae, Gyrinidae, Haliplidae, Hydraenidae, Hydrophilidae, Noteridae, Psephenidae, Ptilodactylidae, Scirtidae) by John H. Epler, Ph.D.
Aquatic Invertebrates of Alberta - Beetles General info, keys to familes and genera, and several dozen photos
