Water Penny (Family Psephenidae)
Water pennies are the larvae of riffle beetles. Water pennies live underwater on rocks in rapid currents—an unusual habitat for a beetle, but one that offers some protection from predators. Adult riffle beetles can be found in the water or basking on rocks and logs just above the water line. The adults are hairy, ¼inch beetles; the larvae, called water pennies for their shape and color, look like well-camouflaged, tiny, suction cups.