Graceful Winter Stonefly vs Trico Mayfly

Side-by-side species comparison

Graceful Winter Stonefly

A minute stonefly of cold North American headwater streams emerging in winter. Females are often short-winged or wingless.

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Females sacrifice flight ability for greater egg production by reducing or eliminating their wings.

A tiny mayfly that forms enormous morning spinner falls over calm streams and rivers. Males have distinctive white bodies with black thoraxes.

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Trico spinner falls create such dense blankets of spent mayflies on the water surface that trout gorge themselves to satiation.