I'm willing to bet pond $$ that they are
damselfly nymphs. Eventually they will crawl out
of the pond, on a reed or sedge or cattail. They will split their outer skin at
the 'neck' and crawl out. They need to hang out and wait for their wings to
dry, then fly off.
They love to mosquitoes, midges and gnats among other flying insects. They will
catch it in flight in a basket like device it makes with its front legs and
then will land on a plant stem to tear up its victim and eat him.
Damselflies are daintier than dragonflies. They will fold their wings back at
rest. Dragonflies have their wings fixed and spread.
The whole process starts again as the females lay their eggs in the pond.


k30a