KINGDOM: Animalia | PHYLUM: Arthropoda | CLASS: Insecta | ORDER: Plecoptera (stoneflies)

Stoneflies have incomplete metamorphosis: eggs are placed in masses on the water surface by adult stoneflies and hatch into naiads.  Naiads may live underwater for a few years before moving to the water surface to molt into winged adults.

Stonefly naiads occur in fast moving streams where they are most commonly found clinging to the undersides of rocks.  Many stonefly naiads are predators, feeding on other aquatic arthropods.  Naiads of other species eat plants and algae.  Although stonefly naiads were once very common in streams, they are very sensitive to pollution.  These days, stonefly naiads are only common in very clean water.  Stonefly adults can't fly very well, and are usually found sitting on rocks near the streams where they emerged.  Many stonefly adults do not feed, others feed on algae, pollen, or other plant parts.  Stoneflies are a very important food source for fish and birds, and they are also eaten by spiders and predatory insects.

Stoneflies are not considered pests.

FAMILIES: Perlidae, Pteronarcidae, and Taeniopterygidae
We have several common stonefly species in Kentucky, but most are very similar in appearance and habits.  Pictured below center is a stonefly adult which has just molted.  Insects are soft and unable to fly for a short time just after they molt, and are said to be in a "teneral" state.

Adult stoneflies usually emerge from the water at very specific times of the year.  Depending on the species, they are very common at certain times of the year, impossible to find at others.  Many common species emerge in the late-spring and early summer, and they are most active at night.  Look for them near fast-flowing streams and lakes.  Stonefly naiads, on the other hand, can be found at almost any time of the year in clean, clear streams.  Stonefly naiads, like all naiads, should be preserved in alcohol.

Unlike some other aquatic insects, stonefly naiads usually do not do well in home aquariums.  Most stoneflies need running water with lots of oxygen - a condition that is difficult to maintain in an aquarium.

Like many aquatic insects, stonefly naiads need clean water to live.  Because of this, scientists can tell if a stream is polluted or not based on whether stonefly naiads are present.  Read more about using insects to determine water quality: http://www.aces.edu/pubs/docs/A/ANR-1167/ANR-1167.pdf

Have you heard any myths, legends, or folklore about stoneflies?  If so, let us know.