J:son Mayfly Dun 2 Olive Grey #12

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 2 Olive Grey (#12)

The Large Olive Specialist – Siphlonurus & Blue-Winged Olive Specialist The J:son Mayfly Dun 2 Olive Grey in size #12 is a technical masterpiece measuring 20 mm. This color is specifically designed to match a wide range of olive-toned and greyish mayflies that dominate river systems worldwide. It is the premier choice for imitating larger Simsländor (Siphlonurus) and dark-bodied Blue-Winged Olives that hatch during overcast or rainy days when fish become notoriously picky.

Why this fly delivers:

• Correct Surface Print: The combination of an extended foam body and precisely shaped upright wings creates the perfect "sail" silhouette. This footprint on the water film is a major strike trigger for selective trout and grayling.

• Optimal Vulnerability: Designed to sit in the surface film exactly like a natural dun struggling to dry its wings, making it an irresistible, easy target for predators.

• Unsinkable Foam Technology: Utilizing J:son’s proprietary foam-body technology, this fly offers incredible buoyancy. It rides high and stable, ensuring it remains visible and effective even in turbulent or broken water.

• Realistic Light Refraction: The air-trapping wings reflect light just like a natural insect wing. This high level of anatomical detail ensures the fly passes the "inspection test" even in crystal-clear water.

Pro Tip: For a 1-2 fly with its realistic wing surface, we highly recommend using a J:son Swivel. The wings can act as a small propeller during casting, which can lead to line twist. Using a swivel ensures a perfect, natural presentation and keeps your leader in top condition.