I often wonder why an extended body mayfly this small works, but it really does. The Baetis Micro Dun is tied as a size 14 imitation to the Baetis Rhodani on a curved hook. The fly gained popularity in Norway after Andrè Brun introduced it in his DVD series “The Trout Bum”. The Baetis Micro Dun is a standard in my fly box, and often used when trout turns selective on the Baetis Rhodani dun.


Extended bodies are heavily used on larger mayflies. There are no reasons why you can’t use them all the way down to size 16. The only thing to remember is to find a chenille that’s slender enough to imitate the natural.

André Brun is a Norwegian that is heavily promoting this fly. He also has a chenille that work well down to size 14. If you wanna tie smaller use the variant I’ve used for the Ignita Spinner.

You can tie the fly both with a poly wing or a CdC. Just make sure you’ll get the profile right.


Hook: TMC 2488 size 12-16
Thread: Benecchi 12/0 Gray (here)
Abdomen: Here André Bruns Polychenille
Hackle: Whiting medium Dun
Wing: Polywing
Thorax: A blend of FlyRite # 26 Adams Grey and #41 Pale Olive (80/20)

Materials are listed in order of tying.

Fishing Tips

Apply floatant to the hackle only and let it float freely without any drag – dead drift. Use a long well tapered leader.