flock of pond skaters in the river backwater

flock insects river backwater pond skater strider aquatic organisms arthropods biology student biophysics broadshouldered striders entwater measurer entomology film force gerridae glowing herd hydrobionts hydrometra inhabitants lakes collection invertebrates lake laws microscopic physics pondskater quiet ripple bugs slip surface tension swarm transparent veliidae water body insect nature wildlife zoology learning