San Juan Worm
Love it or hate it, it catches fish — lots of fish.
The San Juan Worm is the most controversial and most effective simple fly in the game. A tuft of Ultra Chenille or Squirmy Wormy material on a hook, it imitates aquatic worms that trout hoover up after rain events and high water. Purists scoff, but the fish don't care.
History & Lore
Named after New Mexico's San Juan River, where it became infamous in the 1980s. The tailwater below Navajo Dam releases nutrient-rich water that supports enormous populations of aquatic worms (Tubifex and Lumbriculus). Local guides discovered that a simple chenille worm pattern was the most consistent producer on the river.
Variations
Squirmy Wormy
Stretchy silicone material for lifelike wriggling movement.
Beadhead San Juan Worm
Tungsten bead for added weight.
Micro Worm
Tied on #16-18 for pressured tailwater fish.
How to Fish It
Dead drift the San Juan Worm along the bottom during or after rain events, high water, or anytime worms are active. It is especially productive as the lead fly in a double-nymph rig, with a smaller midge or mayfly nymph as the dropper. Don't overthink it.
When to Use
After rainstorms, during high water events, and year-round on tailwaters with worm populations. Particularly effective in winter when trout are sluggish and want an easy meal.
Materials
- Hook
- TMC 2457, #10-16, scud/emerger
- Thread
- Uni 6/0, red or brown
- Body
- Ultra Chenille or Squirmy Wormy, red, pink, or brown
- Bead
- Small tungsten bead, optional
Tying Video
Tying Steps
Place a scud hook in the vise. Optionally slide on a small tungsten bead.
💡 Beadhead versions sink faster in heavy water.
Start thread at the midpoint of the shank.
💡 A few thread wraps is all you need — this is a 30-second fly.
Cut a 2-inch length of Ultra Chenille or Squirmy Wormy material.
💡 Red and pink are the classic colors; brown for more natural presentations.
Tie the material to the hook at the center, so equal lengths extend fore and aft.
💡 Use tight thread wraps to prevent spinning.
Build a small thread bump over the tie-in point. Whip finish and cement.
💡 Singe or taper the ends of the chenille for a natural taper.
Frequently Asked Questions
What size San Juan Worm should I use?
The San Juan Worm is most commonly tied in sizes 10–16. After rainstorms, during high water events, and year-round on tailwaters with worm populations. Particularly effective in winter when trout are sluggish and want an easy meal.
What does a San Juan Worm imitate?
The San Juan Worm primarily imitates aquatic worms, Tubifex worms, earthworms. Dead drift the San Juan Worm along the bottom during or after rain events, high water, or anytime worms are active. It is especially productive as the
What materials do I need to tie a San Juan Worm?
Key materials include: Hook, Thread, Body, Bead. Tie a length of Ultra Chenille or Squirmy Wormy material to a curved hook, extending past both ends.
How do you fish a San Juan Worm?
Dead drift the San Juan Worm along the bottom during or after rain events, high water, or anytime worms are active. It is especially productive as the lead fly in a double-nymph rig, with a smaller midge or mayfly nymph as the dropper. Don't overthink it.
Pattern Details
- Category
- Nymphs
- Sizes
- 10–16
- Colors
- Red, Pink, Brown, Wine
- Weight
- Small tungsten, None
- Hook Styles
- Scud hook, Curved nymph
- Imitates
- aquatic worms, Tubifex worms, earthworms
- Water Types
- tailwater, freestone
- Origin
- San Juan River guides, New Mexico, 1980s
Target Species
Pattern Details
- Category
- Nymphs
- Sizes
- 10–16
- Colors
- Red, Pink, Brown, Wine
- Weight
- Small tungsten, None
- Hook Styles
- Scud hook, Curved nymph
- Imitates
- aquatic worms, Tubifex worms, earthworms
- Water Types
- tailwater, freestone
- Origin
- San Juan River guides, New Mexico, 1980s