Guide

Look closerInsects

Winter stoneflies: insects that emerge from brooks in the cold

January to March

Adult winter stoneflies are dark insects that climb out of clean, rocky streams and crawl across snowy banks in the cold months. Look for them on snow, rocks, and bushes beside a brook on a mild, sunny winter afternoon.

Why this time of year

Adult winter stoneflies emerge from brooks in midwinter, with a peak in February for one species studied in Vermont and New Hampshire, so snow-covered banks are where to find them.

How to notice it

  1. Pick a sunny winter afternoon and stand on the bank of a small, clean, rocky brook, ideally one with some snow beside it.
  2. Scan the snow, bare rocks at the water's edge, and bridge rails or bare bushes and tree trunks near the bank for small dark insects.
  3. Watch how they move. In the cold they tend to crawl rather than fly, so look for slow walkers on the snow surface.
  4. Stay on the bank. Do not step onto ice or into the water to get a closer look.

Try this with kids: Stand still a few steps back from the water's edge and count how many tiny dark insects you can spot walking on the snow. Do they crawl or fly?

Word to know: “Stoneflies” are insects that spend their young stage underwater in streams and leave the water to become winged adults.

Safety

  • Watch from the bank. Do not walk onto stream ice or into cold water.
  • Snowy banks near water can be slippery. Keep a safe distance from the edge.

Sources

  • northernwoodlands.orgNorthern Woodlands: two stonefly families emerge when snow coats riverbanks; in cold, adults more likely crawling than flying; they crawl along riverbank snow; seen on banks of clean rocky streams, most likely on warm afternoons.
  • northernwoodlands.orgNorthern Woodlands: winter stonefly (Taeniopteryx nivalis) emergence begins in January, peaks in February, tapers off in March; adults warm on exposed rocks at the water's edge and alight on bare bushes and tree trunks near the bank.
  • bugoftheweek.comUniversity of Maryland extension column (Mid-Atlantic): best viewing when stream banks are snow-covered; adults on stones, vegetation and bridges near small fast streams.
  • blog.zoonewengland.orgZoo New England blog (secondary): adults emerge in later winter and early spring and walk on snow and ice near the stream edge.

Checked against these sources on October 20, 2026.

In the guide for January, February, March

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