Common Stonefly
Perla bipunctata
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Needs cold, fast, clean, well-oxygenated water — which is why its presence is such good news.
A large, flattened, brownish-yellow insect with two pairs of net-veined wings folded flat along the back at rest, long antennae and two tail filaments. Common stoneflies live along fast, stony, well-oxygenated rivers and burns in the uplands of Dumfries and Galloway, and adults are usually found resting on boulders and bridge parapets close to the water.
Behaviour
Stoneflies are among the most pollution-sensitive of all freshwater insects, needing cold, fast, clean and highly oxygenated water, so river ecologists use their presence as a direct measure of water quality — a burn with stoneflies is in good condition. The predatory nymph lives for two to three years under stones, and adults are weak, reluctant fliers that rarely stray far.
When to see it
Quick facts
- Family
- Common stoneflies (Perlidae)
- Size
- Body 15–25 mm
- Status
- Native; a key indicator of clean, fast-flowing water
Photo by Wlodzimierz, CC BY-SA 4.0, via Wikimedia Commons