![]() ![]() What happens under a water penny, stays under a water penny. In the process, they don’t get whipped away either. ![]() Under the cover of their “shell, they scrape/loosen tiny plants to eat, food that doesn’t get whipped away by the current because it’s trapped under them. So, in summary, these 6mm critters live in strong currents. Hard for us to find, they are said to be eaten by trout living in those same oxygen-rich waters. Water pennies are indicators of waterways that are high in oxygen and low in pollution. The larvae can also absorb oxygen through the general surface of their body. Swift currents tend to be oxygen-rich, and the gills of water pennies grab dissolved oxygen from the active waters they live in. ![]() Head and mouth are located at one end, and its nether end, five pair of gills may be seen. In colder climates, water pennies may overwinter, metamorphosing into adults the next year. The larvae of some species are marginally social. But at night, water pennies migrate to the upper surfaces of the rock where the more nutritious algae grow. They are light-sensitive, clinging by day to the lower surfaces of rocks. Another source said that they have scrapers on their legs. ![]() Their cup-shaped jaws have a sharp inner edge, similar to a paint scraper, to dislodge food, and hairs at the base of the jaws help push the dislodged material into their mouths. Voshell says that to this end, they are well-adapted. Water pennies are classed, diet-wise, as “scrapers” that ingest the algae and diatoms that live on rocks (a moderate algal film is good-a thick algal mat is not water penny-friendly). The edges of the plates are fringed with hairs that enhance its “grip.”Īdult riffle beetles’ basking days are brief, and they probably don’t eat (not much is known about them). The claws on a water penny’s tarsi (BugSpeak for feet) help it latch onto rock surfaces, and the “plates” that make up the tops of its body are flexible, allowing it to mold to the shape of a rock. Her eggs hatch into the characteristic limpet-like larvae that cling tightly to rock surfaces, allowing the water to flow over them. The hairs on her body hold a film of air. Water pennies occur world-wide (the greatest diversity is found in the Orient) and there are 16 species in North America.Īn upside-down water penny is reminiscent of a tiny, cartoon turtle.Ī female riffle beetle crawls “below-decks” into the swift currents to lay her eggs on the lower surfaces of algae-covered rocks, though eggs may also be deposited just above the water’s surface. The adults are hairy, ¼inch beetles the larvae, called water pennies for their shape and color, look like well-camouflaged, tiny, suction cups (the official name for the shape is “platyform”). Adult riffle beetles can be found in the water or basking on rocks and logs just above the water line, and according to Voshell, in the outstanding A Guide to Common Freshwater Invertebrates of North America, adults may also be found on rocks on wave-washed lakeshores. Water pennies live underwater on rocks in rapid currents-an unusual habitat for a beetle, but one that offers some protection from predators. Water pennies are the larvae of riffle beetles in the family Psephenidae (the first “P” is kind of silent, and “ph” = “f”). Some are streamlined, some use glue or silk, others have ways of grabbing their surroundings so they don’t end up a mile downstream. If an animal lives in swift currents, where today’s featured bug hangs out, it has one more problem. They need shelter from organisms that would eat them, the right habitat, and a plan for overwintering. They need a way to breathe, eat and locomote under water. Whether a tadpole, a leech, a snail, or one of the myriad immature insects for whom the water is a nursery, aquatic organisms face some common challenges. Today’s BOTW is one that, like caddisflies, tent caterpillars, and wooly bear caterpillars, has an immature/larval/nymphal stage that is much better known than its adult stage. ![]()
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