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.[1] The adults of most are between 1 and 2.5 cm (0.4–1.0 in) long, though much variation is seen between species. The European Dytiscus latissimus and Brazilian Megadytes ducalis are the largest, reaching up to 4.5 cm (1.8 in) and 4.75 cm (1.9 in) respectively.[1][2] In contrast, the smallest is likely the Australian Limbodessus atypicali of subterranean waters, which only is about 0.9 mm (0.035 in) long.[1] 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.[3] 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.[4]

Dytiscidae
Cybister lateralimarginalis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Adephaga
Superfamily: Dytiscoidea
Family: Dytiscidae
Leach, 1815
Subfamilies

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.[5] Diving beetles live in water bodies in various landscapes, including agricultural and urban landscapes.[6][7][8] Some species, such as Agabus uliginosus[6] and Acilius canaliculatus,[8] are found to be relatively tolerant to recent urbanization.

Larvae and development
A predaceous diving beetle larva ("water tiger")

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.[9] Their usual prey includes tadpoles[10][9] 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.[9]

Edibility

Adult Dytiscidae, particular 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.[11] 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.[12]

Dytiscidae sp.

Large but slow on land, adults are also eaten with relish by many midsized birds, mammals, reptiles, 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. Although not considered particularly fierce, adults have been observed working as a group and attacking much larger vertebrates such as tadpoles.[10]

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.[11]

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.[11]

Parasites

Mites of the genus Dytiscacarus were found to be are highly specialised parasites of beetles in the family Dytiscidae, undergoing their entire life cycle while inhabiting the space beneath the elytra of their hosts.[13]

Systematics

The following taxonomic sequence gives the subfamilies, their associated genera.[14][15][16][17]

Subfamily Agabinae Thomson, 1867

Subfamily Colymbetinae Erichson, 1837

Subfamily Copelatinae Branden, 1885

Subfamily Coptotominae Branden, 1885

Subfamily Cybistrinae

Subfamily Dytiscinae Leach, 1815

Subfamily Hydrodytinae K.B.Miller, 2001

Subfamily Hydroporinae Aubé, 1836

Subfamily Laccophilinae Gistel, 1856

Subfamily Lancetinae Branden, 1885

Subfamily Matinae Branden, 1885

Subfamily †Liadytiscinae Prokin & Ren, 2010

Subfamily Incertae sedis

References
  1. G.N. Foster; D.T. Bilton (2014). "The Conservation of Predaceous Diving Beetles: Knowns, Unknowns and Anecdotes". In D.A. Yee (ed.). Ecology, Systematics, and the Natural History of Predaceous Diving Beetles (Coleoptera: Dytiscidae). pp. 437–462. ISBN 978-94-017-9109-0.
  2. "Archived copy". Archived from the original on 2015-05-21. Retrieved 2015-05-19.CS1 maint: archived copy as title (link)
  3. G.C. McGavin (2010). Insects. pp. 86–87. ISBN 978-1-4053-4997-0.
  4. Nilsson, A.N. (2013). "A World Catalogue of the Family Dytiscidae, or the Diving Beetles (Coleoptera, Adephaga)" (PDF). University of Umeå. Archived from the original (PDF) on 3 April 2018. Retrieved 10 April 2018.
  5. Yee, D.A. (2014). "An Introduction to the Dytiscidae: Their Diversity, Historical Importance, Cultural Significance, and Other Musings". Ecology, Systematics, and the Natural History of Predaceous Diving Beetles (Coleoptera: Dytiscidae). doi:10.1007/978-94-017-9109-0_1.
  6. Lundkvist, E.; Landin, J.; Karlsson, F. (2002). "Dispersing diving beetles (Dytiscidae) in agricultural and urban landscapes in south-eastern Sweden". Annales Zoologici Fennici.
  7. Law, A.; Baker, A.; Sayer, C.; Foster, G.; Gunn, I.D.; Taylor, P.; Blaikie, James; Willby, N.J. (2019). "The effectiveness of aquatic plants as surrogates for wider biodiversity in standing fresh waters". Freshwater Biology. doi:10.1111/fwb.13369.
  8. Liao, W.; Venn, S.; Niemelä, J. (2020). "Environmental determinants of diving beetle assemblages (Coleoptera: Dytiscidae) in an urban landscape". Biodiversity and Conservation. doi:10.1007/s10531-020-01977-9.
  9. Gould, John; Valdez, Jose W.; Clulow, Simon; Clulow, John (2019). "Diving beetle offspring oviposited in amphibian spawn prey on the tadpoles upon hatching". Entomological Science. 22 (4): 393–397. doi:10.1111/ens.12381.
  10. Valdez, Jose W. (2019-08-19). "Predaceous diving beetles (Coleoptera : Dytiscidae) may affect the success of amphibian conservation efforts". Australian Journal of Zoology. 66 (6): 352. doi:10.1071/ZO19039. ISSN 1446-5698.
  11. Miller, Kelly; Bergsten, Johannes (3 October 2016). Diving Beetles of the World: Systematics and Biology of the Dytiscidae. Baltimore: Johns Hopkins University Press. p. 20.
  12. De Foliart (2002), Jäch (2003), CSIRO (2004)
  13. Mortazavi et al. (2018) A new family of mites (Acari: Prostigmata: Raphignathina), highly specialized subelytral parasites of dytiscid water beetles (Coleoptera: Dytiscidae: Dytiscinae). Zoological Journal of the Linnean Society 184 (3): 695–749. https://doi.org/10.1093/zoolinnean/zlx113
  14. "Dytiscidae". GBIF. Retrieved 2019-06-17.
  15. Nilsson, A.N. A World Catalogue of the Family Dytiscidae, or the Diving Beetles (Coleoptera, Adephaga) (PDF) (Report). Archived from the original (PDF) on 2019-07-26. Retrieved 2019-06-18.
  16. Bouchard, Patrice; Bousquet, Yves; Davies, Anthony E.; Alonso-Zarazaga, Miguel A.; et al. (2011). "Family-group names in Coleoptera (Insecta)". ZooKeys (88): 1–972. doi:10.3897/zookeys.88.807. ISSN 1313-2989. PMC 3088472. PMID 21594053.
  17. "Dytiscidae Report". Integrated Taxonomic Information System. Retrieved 2019-06-17.
  • 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.
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