Description
The Mayfly Dun: The Moment of Truth
The stage of the newly hatched adult Mayfly is called the Dun. This is arguably the most critical phase for the fly angler. Depending on surrounding circumstances such as temperature, wind, and weather, the time it takes before the Dun is able to fly away from the surface will vary.
These newly hatched Mayflies are often an easy and vulnerable target for the fish. When the hatching is frequent, many fish species become selective and only feed on Duns. To succeed, your fly needs the right shape, size, proportions, colors, and, not least, the correct footprint on the water.
J:son Mayfly Dun 1 Vanilla Cream (#10)
The Pale Giant Specialist – Ephemera Danica & Hexagenia Expert The J:son Mayfly Dun 1 Vanilla Cream in size #10 is a highly specialized imitation measuring 28 mm. This color profile is specifically engineered to match the lightest phases of our largest mayflies. It is the ultimate choice for the famous Åsandslända (Ephemera danica) and other large, pale mayfly species like the Hexagenia. When the sun is high or the hatch consists of creamy-yellow individuals, this "Vanilla Cream" variant stands out as the perfect anatomical match.
Why this fly delivers:
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The Perfect "Sail" Silhouette: The combination of an extended foam body and large, upright realistic wings creates the exact profile that large trout and grayling are looking for during a massive hatch.
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Unmatched Buoyancy: Built with J:son’s proprietary foam technology, this 28 mm fly is virtually unsinkable. It rides high and proud in the surface film, mimicking a dun waiting for its wings to dry.
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Realistic Light Refraction: The air-trapping wings reflect light in the same way as natural insect wings. This subtle but crucial detail is often what makes the difference when targeting large, selective fish in clear water.
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Vulnerability Trigger: By imitating the vulnerable moment just before takeoff, this fly triggers the predatory instinct of fish that are looking for an easy, high-calorie meal.
Pro Tip: For a fly of this size 1-2, it is essential to use a J:son Swivel. The large, realistic wings can act as a propeller during your cast, which can lead to severe line twist on your leader. A swivel ensures a perfect, natural presentation and protects your tippet.