Dytiscidae

Dytiscidae â€" based on the Greek dytikos (δυτικός), "able to dive" â€" are the predaceous diving beetles, a family of water beetles. They are about 25 mm (one inch) long on average, though there is much variation between species. Dytiscus latissimus, the largest, can grow up to 45 mm long. Most are dark brown, blackish or dark olive in color with golden highlights in some subfamilies. They have short, but sharp mandibles. Immediately upon biting they deliver digestive enzymes. The larvae are commonly known as water tigers. The family has not been comprehensively cataloged since 1920, but is estimated to include about 4,000 species in over 160 genera.

Larvae and development

When still in larval form, the beetles vary in size from about 1 to 5 cm (half an inch to two inches). The larvae's 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 soon-to-be-food between their front legs and biting down with its pincers. Their usual prey includes tadpoles and glassworms, among dozens of other smaller water-dwelling creatures.

As soon as the beetles come to the stage in life in which they mature to adulthood, the larva 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.

Edibility

Adult Dytiscidae, particular of the genus Cybister, are edible. In Mexico, C. explanatus are 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 Dytiscus marginalis are bred for human consumption, though as they are cumbersome to raise due to the 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.

Large but slow on land and not particularly fierce as adults, they are also eaten with relish by many mid-sized birds, mammals and other larger predators. The larvae are usually safer, due to their camouflage and ability to escape by water jet; they can be quite hard to catch and may become apex predators in small ponds.

Systematics

The following taxonomic sequence gives the subfamilies, their associated genera.

Subfamily Agabinae Thomson, 1867

• 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, 1882
• Copelatus Erichson, 1832
• Lacconectus Motschulsky, 1855
• Liopterus Dejean, 1833
• Papuadytes Balke, 1998

Subfamily Coptotominae Branden, 1885

• Coptotomus Say, 1830

Subfamily Dytiscinae Leach, 1815

• Acilius Leach, 1817
• Aethionectes Sharp, 1882
• Austrodytes Watts, 1978
• Cybister Curtis, 1827
• 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
• Prodaticus Sharp, 1882
• Regimbartina Chatanay, 1911
• Rhantaticus Sharp, 1882
• Sandracottus Sharp, 1882
• Spencerhydrus Sharp, 1882
• Sternhydrus Brinck, 1945
• Thermonectus Dejean, 1833
• Tikoloshanes Omer-Cooper, 1956

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
• Andex Sharp, 1882
• Anginopachria Wewalka, Balke & Hendrich, 2001
• Anodocheilus Babington, 1841
• Antiporus Sharp, 1882
• Barretthydrus Lea, 1927
• Bidessodes Régimbart, 1900
• Bidessonotus Régimbart, 1895
• Bidessus Sharp, 1882
• Borneodessus Balke, Hendrich, Mazzoldi & Biström, 2002
• Brachyvatus Zimmermann, 1919
• Calicovatellus K.B.Miller & Lubkin, 2001
• Canthyporus Zimmermann, 1919
• Carabhydrus Watts, 1978
• Celina Aubé, 1837
• Chostonectes Sharp, 1882
• 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
• Geodessus Brancucci, 1979
• Gibbidessus Watts, 1978
• Glareadessus Wewalka & Biström, 1998
• Graptodytes Seidlitz, 1887
• Haideoporus Young & Longley, 1976
• Hemibidessus Zimmermann, 1921
• Heroceras Guignot, 1950
• Herophydrus Sharp, 1882
• Heterhydrus Fairmaire, 1869
• Heterosternuta Strand, 1935
• Hovahydrus Biström, 1982
• Huxelhydrus Sharp, 1882
• Hydrocolus Roughley & Larson, 2000
• Hydrodessus J.Balfour-Browne, 1953
• Hydroglyphus Motschulsky, 1853
• Hydropeplus Sharp, 1882
• Hydroporus Clairville, 1806
• Hydrovatus Motschulsky, 1853
• Hygrotus Stephens, 1828
• Hyphoporus Sharp, 1882
• Hyphovatus Wewalka & Biström, 1994
• Hyphydrus Illiger, 1802
• Hypodessus Guignot, 1939
• Iberoporus Castro & Delgado, 2001
• Kintingka Watts & Humphreys, 1999
• Kuschelydrus Ordish, 1976
• 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
• Neobidessus Young, 1967
• Neoclypeodytes Young, 1967
• Neoporus Guignot, 1931
• Nirripirti Watts & Humphreys, 2001
• Oreodytes Seidlitz, 1887
• Pachydrus Sharp, 1882
• Pachynectes Régimbart, 1903
• Papuadessus Balke, 2001
• Paroster Sharp, 1882
• Peschetius Guignot, 1942
• Phreatodessus Ordish, 1976
• Platydytes Biström, 1988
• Porhydrus Guignot, 1945
• Primospes Sharp, 1882
• Procoelambus Théobald, 1937
• Pseuduvarus Biström, 1988
• 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
• Sternopriscus Sharp, 1882
• 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

Subfamily Laccophilinae Gistel, 1856

• Agabetes Crotch, 1873
• Africophilus Guignot, 1948
• 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 Incertae sedis

• Cretodytes Ponomarenko, 1977
• Palaeodytes Ponomarenko, 1987

Footnotes

References

• Commonwealth Scientific and Industrial Research Organisation (CSIRO) (2004): Water for a Healthy Country - Family Dytiscidae. Version of 2004-JUL-02. Retrieved 2008-AUG-04
• De Foliart, Gene R. (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.
• Jäch, Manfred A. (2003): Fried water beetles Cantonese style. American Entomologist 49(1): 34-37. PDF fulltext
• Larson, D.J., Alarie, Y., and Roughley, R.E. (2000): Predaceous Diving Beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska. NRC Research Press, Ottawa. ISBN 978-0-660-17967-4.

External links

• Video of the dangerous mandibles of a Dytiscidae larva