Winter Stoneflies do their growing and maturing during the coldest seasons of the year. In autumn and winter, when water temperatures cool down in streams, river, and lakes, the deeper, oxygen-rich water near the bottom is finally able to mix with the now colder surface water. This means that any aquatic life that requires lots of oxygen dissolved in water can expand their territory. Winter Stoneflies are insects whose aquatic larvae spend their lives in bodies of water like rivers and streams. They are also dependent on highly oxygenated water to survive, so their ability to withstand and even thrive in cold temperatures allows them to take advantage of improved conditions in their habitat when most other aquatic insects are absent.
Adults mate in late winter, and females lay fertilized eggs in the water. Stoneflies have only a week or two to reproduce before their short lives are spent. The hatched nymphs feed for a short time and then enter a form of hibernation during spring and summer. They resume activity in the cooler months, molting between 10 to 24 times before crawling out of the water to become a winged adult. The hard shells of their nymph bodies, called exuviae, are often seen near the water's edge and look like pale, little crustaceans. As a mature adult, this generation of Winter Stoneflies finds mates and repeats the cycle, ensuring a population continues in that area year after year.
The nymphs of stoneflies are very sensitive to pollution in water, dying in streams and rivers with seemingly little contamination. This means the presence of Stoneflies is a sign of pristine water, and the insect should be a welcome annual sighting.
Scientific Name: Various spp.
Other Name(s): Willowfly
Size (Adult; Length): 2mm to 15mm (0.08in to 0.59in)
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