Stoneflies are not true flies, they have their own order called Plecoptera. Stonefly nymphs are aquatic and the adults are terrestrial. They are almost always found near running water and being rather delicate organisms only clean running water. 

The early emerging stoneflies are in the family Taeniopterygidae and are commonly called winter stoneflies, willowflies, early browns or black stoneflies. 

The adults of these winter stoneflies emerge at night in the late winter, early spring and feed on algae, lichen and flower pollen. They have short adult lives ranging from a week to a few weeks, longer at least than Mayflies. 

Male stoneflies have an interesting way of flirting or communicating with the females for mating. They signal through substrates. The males use their abdomen to create complex stridulations, drummings and tapping on different substrates the female has landed on. The complexity of these rhythms are species specific, similar to the flashes of fireflies. This complexity is a great example of natural selection at work. The males also congregate and fly around the females to get their attention. Here sexual selection by the female comes into play. She will choose to mate with the male with the best flight patterns and most complex stridulations which reflects his fitness. This fitness will in turn be passed on to her offspring.

Once the female has mated, her goal is to get her eggs to the water. She does this by gluing them together in a clump and dropping them from the air into the water, or touching the top of the water and dropping the eggs, and in some species the female dives into the water and glues the eggs to rocks. Perhaps you have seen this, many small flying insects tapping the water top with their abdomens. It’s a dangerous feat. Both the stonefly and the eggs are a high protein food source to many fish and a vital source in the food web. Thus the strategy of the stoneflies, as in many R species, invest little in the offspring and produce many, is to do it in large numbers at the same time to ensure some of the eggs make it to the water. 

For those eggs that do survive and hatch, a potentially long aquatic life may ensue. Stonefly nymphs molt anywhere from 10-30 times. The time between each molt is called an instar. And interestingly each instar comes with new fangled body parts. These new additions range from new antennal segments, gills, body hairs and abdominal segments. Most importantly their mouthparts change from scraping ridges to sharp teethlike mandibles for grabbing and devouring prey whole. This growing process can take one to four years depending on the species. With all these body modifications the food sources the nymphs feed on changes too. They start feeding on detritus then become predatory on other aquatic insects, but may eat plants and algae. Think about it, these changing characteristics will help it survive and grow into an adult and allow them to gain the energy needed to escape larger predators, like the helgramites, but that’s a different story. And as any fly fisherman knows, these stonefly nymphs are prime eating for fish.

When the nymph, also called a naiad, is ready for its final molt into adulthood, it climbs from the water onto a rock, or plant stem or structure such as a guardrail or bridge support, and sheds its larval skin. If you start looking closely you will find these sheds along with the dragonfly sheds. The final larva performs its final molt through a weakened crease in the exoskeleton which starts at the head and down the thoracic segments. This weakness in the exoskeleton is called the “line of ecdysis”. Ecdysis is the process of shedding of the exoskeleton. Once it’s free of the last exoskeleton, it’s free to fly about and start the cycle of life again.