Published Apr 21. 2014 - 8 years ago
Updated or edited Feb 9. 2016

OSA Nymph

A generic nymph that can do equally well as a stonefly or mayfly nymph as it can a waterboatman or backswimmer

Different sizes - The OSA nymph can be tied in various sizes
OSA nymphs
Korrie Broos

This fly have caught many trout and yellowfish for me, over the last couple of years.
It is one of my 4 or 5 top goto flies, and when I start fishing I often tie on an OSA Nymph.
It is a general mayfly to stonefly nymph profile. The black bead and abdomen, gives a very good profile against any background and in any light conditions, with the UV dubbing add a different depth, dimension in the light and in the light spectrum.

I paged thru some old magazines, the other day, and saw the TVN nymph, and thought there is something similar to the profile and color of the TVN nymph, what could be another reason for doing so well with the yellows.

Backswimmer - The OSA nymph is an excellent water boatman (corixa) or backswimmer (notonectida) imitation
Wikimedia, Piet Spaans

It has also produced a good number of fish on still waters. When I was looking at the water boatmen, backswimmers and corixia images on the net the other day, I realised why. The basic profile is very close to the water boatmen, backswimmers and corixia. But the UV thorax, makes a very good air bubble impersonation.

Perhaps, for most fish, it looks, just too much like food, to not taste it.

What's OSA for a name anyway?

OSA is a fly named after the Old South Africa (apartheid, definite segregation etc). The fly being distinctly black and white mixed with brownish colors it's a reflection of SA as it was. We had black people, white people, the copper wire was for the Indian/curry and the pheasant tail was the colored or brown people (people with mixed parents, black and white) and the tungsten bead is all the hard headed people in South Africa.
All of this might not make sense if you don't know too much about SA, apartheid etc.

OSA Nymph
Pattern type: 
Korrie Broos
#8 to 18
Black or gun metal black
Lead or tungsted wire
6 to 10 Pheasant tail barbs, depending on the size of the fly
Copper wire
Black possum or squirrel dubbing
White UV Dubbing
Skill level/difficulty: 
  1. Place bead behind hook eye, and wrap the optional lead wire behind bead.
  2. Tie in Pheasant tail in as tail and leave the long butt section, as this will become the legs.
  3. Tie in the copper wire.
  4. Apply dubbing and wrap over the pheasant tail fibres, to about two-thirds up the hook shank.
  5. Rib with copper wire and tie off copper wire.
  6. Lift pheasant tail fibres up and dub thread and under the pheasant tail fibres to bead.
  7. Backward and forward wrapping of the UV dubbing can be done, to attain the right density, covering shape of thorax.
  8. Take pheasant tail barbs over UV dubbed thorax and tie in with 2 or 3 wraps behind the bead.
  9. Split barbs in equal numbers and fold to either side of bead/body.
  10. Tie the barbs in at about 45 degrees to body and whip finish.
  11. Trim the barbs about two-thirds of the overall length of fly.

Step 1 - tail, rib, herl

Step 2 - weight

Step 3 - wrap herl

Step 4 - rib

Step 5 - thorax

Step 6 - wing case

Step 7 - separate herl

Step 8 - pull down

Step 9 - ready to trim

OSA Nymphs - Top view showing the back and legs
OSA Nymphs - The underside with the clear flashy thorax
Top and bottom
Korrie Broos
Nymphing - The author on the stream
The originator - Korrie Bros with a nice SA rainbow
The author and originator
Korrie Broos


Tony, this fly is eq...

Tony, this fly is equally at home in stillwaters and rivers. The profile, shape and size can be so many insects, that fish very seldom swims past it, without taking a nibble

It seems to me this ...

It seems to me this fly would be primarily for stillwater or do you find it equally at home on rivers?


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