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Green Rock Worm / Green Weenie (Rhyacophila spp.)

Caddis, hatching April–June and September–October, active in water between 45 and 68°F, and imitated at #10–14. Recorded from the Virginia mountains, where 796 Virginia rivers on this site carry a page.

Green Rock Worm / Green Weenie, Rhyacophila spp.
Rhyacophila grandis 01 — Libby Avis, Centre for Biodiversity Genomics, CC0, via Wikimedia Commons.
Subbasins with trout water where it is on record: 29 of Virginia's 53.
See Virginia's trout water on the live map → Every reach coloured by water temperature — the water these hatches come off.

What it is

Caddis · Rhyacophila spp. · larva

A bright green, clearly segmented caddis larva with a dark shiny head and a pair of hooked anal prolegs. It builds no case and carries no shelter, so it is naked on the rock and unmistakable when turned up.

The free-living larva of the green sedge, and the only caddis in these waters that builds no case — it crawls the rock exposed and is in the drift constantly. Fished dead-drift and deep, never swung. The Appalachian Green Weenie is the folk version of the same bug and outfishes far more sophisticated flies.

When it hatches

Peak is April–June and September–October. The pale months either side are the shoulder — the app widens a peak by one month in each direction and recommends the bug there, and no further: that widening is bounded so that a bug peaking in May is never offered in August.

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peak shoulder not recommended

Water conditions

The band is a water temperature, not an air temperature, and it is the range in which this insect is worth fishing — for a mayfly that is the emergence window; for a scud or a midge it is simply the range trout will still eat one in.

45°F 68°F

Active from 45°F to 68°F. On this map that is cold, cold-transitional, cool water — the band crosses 2 of the three breaks the river colours use. Breaks at 58, 64 and 70°F.

Stages

What the insect is doing, and what that means for what you tie on.

StageWhat it is
larva Free-living, crawling over the tops of stones hunting other insects, and constantly washed loose. This is the whole of the fishing: dead-drift, deep, on a tight line. The Appalachian Green Weenie is a folk-simplified version of it, and outfishes flies with ten times the tying in it.

Matching flies

5 patterns in this book imitate the Green Rock Worm / Green Weenie, across its stages. Which one to tie on follows the stage the water temperature says it is in — the app makes that call on a live reading; this page lists the whole set.

Where to find it right now

The rivers with a page here that sit in this insect's regions, with a USGS gauge reporting water temperature. This list is re-ranked against the reading each gauge is sending now and today's date, so it is live — the fallback below it, if the readings do not arrive, is each river's measured July mean.

Regional presence

Regions, not collection records. This insect is recorded from the coarse regions below; nobody has surveyed which named river it has been caught on, and this page will not pretend otherwise.

Rivers in these regions with a page here

Related hatches

Same family, or overlapping this one's calendar on the same water.

Open the trout map →Every trout stream near you, coloured by today's water temperature.