Who is this tiny creature walking atop a snowy streambank?
An adult winter stonefly is on the move!
Winter stoneflies spend most of their life as nymphs in streams. They have hooks on their legs to cling to rocks, finger-like gills to absorb oxygen (their small gills make them sensitive to pollution), and cutting mouthparts to eat midge larvae, mayfly nymphs, and other stream insects.
Winter stonefly nymph
On sunny days around January through April, winter stonefly nymphs crawl through cracks in the ice and snow coating their watery homes. They shed their skin a final time and emerge as winged adults, still with two long tail filaments. Winter stonefly adults have a mix of antifreeze compounds (glycerol, proteins, and sugars) that allow body fluids to remain unfrozen at temperatures even lower than the nymphs – as low as -40F!
Adults may live just a few days and have one goal – mating. To find each other, males drum their bodies in a specific pattern and females drum in response.
The next day, females drop several thousand eggs into the water, where only a few may land in just the right way under stones to avoid predation and continue the next generation.