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 Olive Grey (#10)
The Large Selective Specialist – Green Drake & Ephemera Specialist The J:son Mayfly Dun 1 Olive Grey in size #10 is a powerhouse imitation measuring a massive 28 mm. This specific color profile is designed to match the larger, darker mayfly species found in both rivers and lakes. The Olive Grey hue is particularly effective for mimicking the "Eastern Green Drake" (Ephemera guttulata) or darker variations of the European Ephemera species when the light is low or the hatch consists of more olive-toned individuals.
Why this fly delivers:
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Correct Surface Print: The combination of the extended foam body and the large, upright wings creates a perfect "sail" silhouette. This specific footprint on the water film is what triggers a response from the most cautious, trophy-sized fish.
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Virtually Unsinkable: Utilizing J:son’s specialized foam technology, this 28 mm fly provides unmatched buoyancy. It sits high in the surface film, mimicking a dun waiting for its wings to dry—the ultimate "vulnerability" signal to a predator.
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Natural Light Refraction: The realistically printed wings are designed to trap air and reflect light exactly like natural insect wings. This level of anatomical detail ensures that the fly passes the "inspection test" in clear water.
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Exceptional Durability: Unlike traditional feather-wing flies that become matted and useless after one fish, J:son’s materials are built to withstand multiple aggressive strikes while maintaining their shape and floating properties.
Pro Tip: For a fly of this size 1-2, it is essential to use a J:son Swivel. The large wing surface can cause the fly to spin like a propeller during casting, leading to severe line twist. A swivel ensures a natural, drag-free presentation and keeps your leader in perfect condition for when that monster trout finally rises.