Dytiscidae

Dytiscidae
The Dytiscidae – based on the Greek dytikos (δυτικός), "able to dive" – are the predaceous diving beetles, a family of water beetles. They occur in virtually any freshwater habitat around the world, but a few species live among leaf litter. The adults of most are between long, though much variation is seen between species. The European Dytiscus latissimus and Brazilian Megadytes ducalis are the largest, reaching up to and respectively. In contrast, the smallest is likely the Australian Limbodessus atypicali of subterranean waters, which only is about long. Most are dark brown, blackish, or dark olive in color with golden highlights in some subfamilies. The larvae are commonly known as water tigers due to their voracious appetite. They have short, but sharp mandibles and immediately upon biting, they deliver digestive enzymes into prey to suck their liquefied remains. The family includes more than 4,000 described species in numerous genera.
Habitat
Diving beetles are the most diverse beetles in the aquatic environment and can be found in almost every kind of freshwater habitat, from small rock pools to big lakes. Some dytiscid species are also found in brackish water. Diving beetles live in water bodies in various landscapes, including agricultural and urban landscapes. Some species, such as Agabus uliginosus and Acilius canaliculatus, are found to be relatively tolerant to recent urbanization. One of the most important limiting factors for diving beetle occurrence is the presence of fish, which predate on the beetles (mostly on larvae), compete for food, and change the structure of the habitat. Many diving beetles species prefer habitats with aquatic vegetation, while some species, such as Oreodytes sanmarkii, occur in exposed areas of waters.
Larvae and development
When still in larval form, the beetles vary in size from about 1 to 5 cm (0.5 to 2.0 in). The larval bodies are shaped like crescents, with the tail long and covered with thin hairs. Six legs protrude from along the thorax, which also sports the same thin hairs. The head is flat and square, with a pair of long, large pincers. When hunting, they cling to grasses or pieces of wood along the bottom, and hold perfectly still until prey passes by, then they lunge, trapping their prey between their front legs and biting down with their pincers. The larvae are also known to partially consume prey and discard the carcass if another potential prey swims nearby. Their usual prey includes tadpoles and glassworms, among other smaller water-dwelling creatures. As the larvae mature, they crawl from the water on the sturdy legs, and bury themselves in the mud for pupation. After about a week, or longer in some species, they emerge from the mud as adults. Adult diving beetles have been found to oviposit their eggs within frog spawn in highly ephemeral habitats, with their eggs hatching within 24 hours after the frogs and the larvae voraciously predating on the recently hatched tadpoles.
Edibility
Adult Dytiscidae, particularly of the genus Cybister, are edible. Remnants of C. explanatus were found in prehistoric human coprolites in a Nevada cave, likely sourced from the Humboldt Sink. In Mexico, C. explanatus is eaten roasted and salted to accompany tacos. In Japan, C. japonicus has been used as food in certain regions such as Nagano prefecture. In the Guangdong Province of China, the latter species, as well as C. bengalensis, C. guerini, C. limbatus, C. sugillatus, C. tripunctatus, and probably also the well-known great diving beetle (D. marginalis) are bred for human consumption, though as they are cumbersome to raise due to their carnivorous habit and have a fairly bland (though apparently not offensive) taste and little meat, this is decreasing. Dytiscidae are reportedly also eaten in Taiwan, Thailand, and New Guinea.
Diving beetle conservation
The greatest threat to diving beetles is the degradation and disappearance of their habitats due to anthropogenic activities. For example, urbanisation has led to the decreasing quantity and quality of dytiscid habitats, which consequentially has increased the distance between habitats. Thus, dytiscids may be exposed to high predation risks during dispersal.
Dytiscid adults are eaten by many birds, mammals, reptiles, and other vertebrate predators, despite their arsenal of chemical defenses. But by far the most important predator of diving beetles are fish, which limit the occurrence of most diving beetle species to fishless ponds, or to margins of aquatic habitats. Although the larvae of a few dytiscid species may become apex predators in small ponds, their presence is also often incompatible with fish. Therefore, the main focus of water beetle conservation is the protection of natural, fish-less habitats.
In the European Union, two species of diving beetles are protected by the Berne Convention on the Conservation of European Wildlife and Natural Habitats, and thus serve as umbrella species for the protection of natural aquatic habitats: Dytiscus latissimus and Graphoderus bilineatus.
Cultural significance
The diving beetle plays a role in a Cherokee creation story. According to the narrative, upon finding nowhere to rest in the "liquid chaos" the beetle brought up soft mud from the bottom. This mud then spread out to form all of the land on Earth.
Ethnobiology
Adult Dytiscidae, as well as Gyrinidae, are collected by young girls in East Africa. It is believed that inducing the beetles to bite the nipples will stimulate breast growth. The effect of that habit has not been tested, but it is notable that the defense glands of diving beetles contain many types of bioactive steroids.
Parasites
Dytiscidae are parasitised by various mites. Those in genera Dytiscacarus and Eylais live beneath the elytra of their hosts, those in genus Acherontacarus attach to the mesosternal regions and those in genus Hydrachna attach to various locations. These mites are parasitic as larvae with the exception of Dytiscacarus, which are parasitic for their entire life cycle.
Systematics
The following taxonomic sequence gives the subfamilies, their associated genera.
Subfamily Agabinae Thomson, 1867
Agabinus Crotch, 1873
Agabus Leach, 1817
Agametrus Sharp, 1882
Andonectes Guéorguiev, 1971
Hydronebrius Jakovlev, 1897
Hydrotrupes Sharp, 1882
Ilybiosoma Crotch, 1873
Ilybius Erichson, 1832
Leuronectes Sharp, 1882
Platambus Thomson, 1859
Platynectes Régimbart, 1879
Subfamily Colymbetinae Erichson, 1837
Anisomeria Brinck, 1943
Senilites Brinck, 1948
Carabdytes Balke, Hendrich & Wewalka, 1992
Bunites Spangler, 1972
Colymbetes Clairville, 1806
Hoperius Fall, 1927
Meladema Laporte, 1835
Melanodytes Seidlitz, 1887
Neoscutopterus J.Balfour-Browne, 1943
Rhantus Dejean, 1833
Rugosus García, 2001
Subfamily Copelatinae Branden, 1885
Agaporomorphus Zimmermann, 1921
Aglymbus Sharp, 1880
Copelatus Erichson, 1832
Exocelina Broun, 1886
Lacconectus Motschulsky, 1855
Liopterus Dejean, 1833
Madaglymbus Shaverdo & Balke, 2008
Rugosus García, 2001
Subfamily Coptotominae Branden, 1885
Coptotomus Say, 1830
Subfamily Cybistrinae
Austrodytes Watts, 1978
Cybister Curtis, 1827
Megadytes Sharp, 1882
Onychohydrus Schaum & White, 1847
Regimbartina Chatanay, 1911
Spencerhydrus Sharp, 1882
Sternhydrus Brinck, 1945
Subfamily Dytiscinae Leach, 1815
Acilius Leach, 1817
Aethionectes Sharp, 1882
Austrodytes Watts, 1978
Dytiscus Linnaeus, 1758
Eretes Laporte, 1833
Graphoderus Dejean, 1833
Hydaticus Leach, 1817
Hyderodes Hope, 1838
Megadytes Sharp, 1882
Miodytiscus Wickham, 1911
Notaticus Zimmermann, 1928
Onychohydrus Schaum & White, 1847
Regimbartina Chatanay, 1911
Rhantaticus Sharp, 1880
Sandracottus Sharp, 1882
Spencerhydrus Sharp, 1882
Sternhydrus Brinck, 1945
Thermonectus Dejean, 1833
Tikoloshanes Omer-Cooper, 1956
†Ambarticus Yang et al. 2019 Burmese amber, Myanmar, Late Cretaceous (Cenomanian)
Subfamily Hydrodytinae K.B.Miller, 2001
Hydrodytes K.B.Miller, 2001
Microhydrodytes K.B.Miller, 2002
Subfamily Hydroporinae Aubé, 1836
Africodytes Biström, 1988
Agnoshydrus Biström, Nilsson & Wewalka, 1997
Allodessus Guignot, 1953
Allopachria Zimmermann, 1924
Amarodytes Régimbart, 1900
Amurodytes Fery & Petrov, 2013
Andex Sharp, 1882
Anginopachria Wewalka, Balke & Hendrich, 2001
Anodocheilus Babington, 1841
Antiporus Sharp, 1882
Barretthydrus Lea, 1927
Bidessodes Régimbart, 1895
Bidessonotus Régimbart, 1895
Bidessus Sharp, 1882
Boreonectes Angus, 2010
Borneodessus Balke, Hendrich, Mazzoldi & Biström, 2002
Brachyvatus Zimmermann, 1919
Brancuporus Hendrich, Toussaint & Balke, 2014
Canthyporus Zimmermann, 1919
Carabhydrus Watts, 1978
Celina Aubé, 1837
Chostonectes Sharp, 1880
Clypeodytes Régimbart, 1894
Coelhydrus Sharp, 1882
Comaldessus Spangler & Barr, 1995
Crinodessus K.B. Miller, 1997
Darwinhydrus Sharp, 1882
Deronectes Sharp, 1882
Derovatellus Sharp, 1882
Desmopachria Babington, 1841
Dimitshydrus Uéno, 1996
Ereboporus K.B. Miller, Gibson & Alarie, 2009
Etruscodytes Mazza, Cianferoni & Rocchi, 2013
Fontidessus K.B. Miller & Spangler, 2008
Geodessus Brancucci, 1979
Gibbidessus Watts, 1978
Glareadessus Wewalka & Biström, 1998
Graptodytes Seidlitz, 1887
Haideoporus Young & Longley, 1976
Hemibidessus Zimmermann, 1921
Heroceras Guignot, 1949
Herophydrus Sharp, 1880
Heterhydrus Fairmaire, 1869
Heterosternuta Strand, 1935
Hovahydrus Biström, 1982
Huxelhydrus Sharp, 1882
Hydrocolus Roughley & Larson in Larson, Alarie & Roughley, 2000
Hydrodessus J. Balfour-Browne, 1953
Hydroglyphus Motschulsky, 1853
Hydropeplus Sharp, 1882
Hydroporus Clairville, 1806
Hydrovatus Motschulsky, 1853
Hygrotus Stephens, 1828
Hyphoporus Sharp, 1880
Hyphovatus Wewalka & Biström, 1994
Hyphydrus Illiger, 1802
Hypodessus Guignot, 1939
Iberoporus Castro & Delgado, 2001
Incomptodessus K.B. Miller & García, 2011
Kakadudessus Hendrich & Balke, 2009
Laccornellus Roughley & Wolfe, 1987
Laccornis Gozis, 1914
Leiodytes Guignot, 1936
Limbodessus Guignot, 1939
Liodessus Guignot, 1939
Lioporeus Guignot, 1950
Megaporus Brinck, 1943
Metaporus Guignot, 1945
Methles Sharp, 1882
Microdessus Young, 1967
Microdytes J. Balfour-Browne, 1946
Morimotoa Uéno, 1957
Nebrioporus Régimbart, 1906
Necterosoma W.J. Macleay, 1871
Neobidessodes Hendrich & Balke, 2009
Neobidessus Young, 1967
Neoclypeodytes Young, 1967
Neoporus Guignot, 1931
Oreodytes Seidlitz, 1887
Pachydrus Sharp, 1882
Pachynectes Régimbart, 1903
Papuadessus Balke, 2001
Paroster Sharp, 1882
Peschetius Guignot, 1942
Petrodessus K.B. Miller, 2012
Phreatodessus Ordish, 1976
Platydytes Biström, 1988
Porhydrus Guignot, 1945
Primospes Sharp, 1882
Pseuduvarus Biström, 1988
Psychopomporus Jean, Telles & K.B. Miller, 2012
Pteroporus Guignot, 1933
Queda Sharp, 1882
Rhithrodytes Bameul, 1989
Sanfilippodytes Franciscolo, 1979
Scarodytes Gozis, 1914
Schistomerus Palmer, 1957
Sekaliporus Watts, 1997
Sharphydrus Omer-Cooper, 1958
Siamoporus Spangler, 1996
Siettitia Abeille de Perrin, 1904
Sinodytes Spangler, 1996
Spanglerodessus K.B. Miller & García, 2011
Sternopriscus Sharp, 1880
Stictonectes Brinck, 1943
Stictotarsus Zimmermann, 1919
Stygoporus Larson & LaBonte, 1994
Suphrodytes Gozis, 1914
Tepuidessus Spangler, 1981
Terradessus Watts, 1982
Tiporus Watts, 1985
Trichonectes Guignot, 1941
Trogloguignotus Sanfilippo, 1958
Tyndallhydrus Sharp, 1882
Typhlodessus Brancucci, 1985
Uvarus Guignot, 1939
Vatellus Aubé, 1837
Yola Gozis, 1886
Yolina Guignot, 1936
† Calicovatellus K.B. Miller & Lubkin, 2001
† Kuschelydrus Ordish, 1976
† Procoelambus Théobald, 1937
Subfamily Laccophilinae Gistel, 1856
Africophilus Guignot, 1948
Agabetes Crotch, 1873
Australphilus Watts, 1978
Japanolaccophilus Satô, 1972
Laccodytes Régimbart, 1895
Laccophilus Leach, 1815
Laccoporus J. Balfour-Browne, 1939
Laccosternus Brancucci, 1983
Napodytes Steiner, 1981
Neptosternus Sharp, 1882
Philaccolilus Guignot, 1937
Philaccolus Guignot, 1937
Philodytes J. Balfour-Browne, 1939
Subfamily Lancetinae Branden, 1885
Lancetes Sharp, 1882
Subfamily Matinae Branden, 1885
Allomatus Mouchamps, 1964
Batrachomatus Clark, 1863
Matus Aubé, 1836
Subfamily †Liadytiscinae Prokin & Ren, 2010
† Liadroporus Prokin & Ren, 2010 Yixian Formation, China, Early Cretaceous (Aptian)
† Liadytiscus Prokin & Ren, 2010 Yixian Formation, China, Aptian
† Mesoderus Prokin & Ren, 2010 Yixian Formation, China, Aptian
† Liadyxianus Prokin, Petrov, B. Wang & Ponomarenko, 2013 Yixian Formation, China, Aptian
† Mesodytes Prokin, Petrov, Wang & Ponomarenko, 2013 Yixian Formation, China, Aptian
Subfamily Incertae sedis
† Cretodytes Ponomarenko, 1977 Doronino Formation, Russia, Early Cretaceous (Barremian), Kzyl-Zhar, Kazakhstan, Late Cretaceous (Turonian)
† Palaeodytes Ponomarenko, 1987 Karabastau Formation, Kazakhstan, Late Jurassic (Oxfordian), Durlston Formation, United Kingdom, Early Cretaceous (Berriasian), Zaza Formation, Russia, Aptian
† Sinoporus Prokin & Ren, 2010 Yixian Formation, China, Aptian
References
(2004): Water for a Healthy Country - Family Dytiscidae. Version of 2004-JUL-02. Retrieved 2008-AUG-04
(2002): Chapter 26 - Eastern Asia: China, Japan, and other countries. In: The Human Use of Insects as a Food Resource: A Bibliographic Account in Progress.
(2003): Fried water beetles Cantonese style. American Entomologist 49(1): 34-37. PDF fulltext
(2000): Predaceous Diving Beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska. NRC Research Press, Ottawa. .
External links
Beetle families
Aquatic insects