Notonectidae is a

cosmopolitan Cosmopolitan may refer to: Internationalism * World citizen, one who eschews traditional geopolitical divisions derived from national citizenship * Cosmopolitanism, the idea that all of humanity belongs to a single moral community * Cosmopolitan ...

family of aquatic insects in the order

Hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising more than 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from ...

, commonly called backswimmers because they swim "upside down" (inverted). They are all

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s and typically range from in length. They are similar in appearance to Corixidae (water boatmen), but can be separated by differences in their dorsal-ventral coloration, front legs, and predatory behavior. Their dorsum is convex, lightly colored without cross striations. Their front tarsi are not scoop-shaped and their hind legs are fringed for swimming. There are about 350 species in two subfamilies: Notonectinae with seven

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

, and Anisopinae with four genera. Members in the former subfamily are often larger than those in the latter. Backswimmers swim on their backs, vigorously paddling with their long, hair-fringed hind legs and attack prey as large as

tadpole A tadpole or polliwog (also spelled pollywog) is the Larva, larval stage in the biological life cycle of an amphibian. Most tadpoles are fully Aquatic animal, aquatic, though some species of amphibians have tadpoles that are terrestrial animal, ...

s and small fish. They can inflict a painful "bite" on a human being, actually a stab with their sharp tubular mouthparts (

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

). They inhabit still freshwater, e.g. lakes, ponds, marshes, and are sometimes found in garden ponds and even swimming pools. Although primarily aquatic, they can fly well and so can disperse easily to new habitats. Notonecta glauca01

The best-known genus of backswimmers is '' Notonecta'' – streamlined, deep-bodied bugs up to long, green, brown, or yellowish in colour. The common backswimmer, '' N. glauca'', is widespread in Europe, including the United Kingdom where it is known as the greater water boatman. Another of the same region, '' N. maculata'', is distinguished by its mottled brick-coloured forewings. In contrast to other aquatic insects that cling to submerged objects, the two genera ''Anisops'' and ''Buenoa'' uses a unique system to stay submerged: using the extra oxygen supply from

haemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobi ...

in their abdomen, instead of using oxygen dissolved in the water. The size of these air bubbles, which provide buoyancy, changes as the nitrogen dissolves into the blood and the oxygen is used in respiration. This allows for regulation of the size of the air bubbles and their concentration of oxygen.

Notes

References

*Chinery, M. (1986). ''Collins Guide to the Insects of Britain & Western Europe''. Collins. . *Fitter, R. & Manuel, R. (1986). ''Collins Field Guide to Freshwater Life''. Collins. . *Hungerford, H. B. (1933). The genus ''Notonecta'' of the world. ''U. Kansas Sci. Bull.'' 21: 5-195.6+516+2kkig
Painful bug bite
Williams 1980, Hawking & Smith 1997
Notonectidae
Australian Freshwater Invertebrates

External links

Notonectidae
BugGuide
BBC Radio special on the sounds made by water boatmen
Nepomorpha Heteroptera families {{Nepomorpha-stub