water beetle

{{Short description|Common name for any beetle living in water}}

File:EB 1911 Water Beetles.png

A water beetle is a generalized name for any beetle that is adapted to living in water at any point in its life cycle. Most water beetles can only live in fresh water, with a few marine species that live in the intertidal zone or littoral zone. There are approximately 2000 species of true water beetles native to lands throughout the world.{{Cite web|url=https://www.everythingabout.net/articles/biology/animals/arthropods/insects/beetles/water_beetle/|title=Water Beetle: pictures, information, classification and more|website=www.everythingabout.net}}

Many water beetles carry an air bubble, called the elytra cavity, underneath their abdomens, which provides an air supply, and prevents water from getting into the spiracles.{{Cite web|url=https://animalcorner.co.uk/animals/water-beetle/|title=Water Beetle - Facts, Information & Pictures}} Others have the surface of their exoskeleton modified to form a plastron, or "physical gill", which permits direct gas exchange with the water. Some families of water beetles have fringed hind legs adapted for swimming, but most do not. Most families of water beetles have larvae that are also aquatic; many have aquatic larvae and terrestrial adults.{{Cite book|title = Freshwater macroinvertebrates of northeastern North America|last = Peckarsky|first = Barbara Lynn|publisher = Comstock Pub. Associates|year = 1990|isbn = 0801420768|location = the University of Michigan}}{{Cite book|title = Aquatic Entomology: The Fishermen's and Ecologists' Illustrated Guide to Insects and Their Relatives|last = McCafferty|first = W. Patrick|publisher = Jones & Bartlett Learning|year = 1983|isbn = 9780867200171}}