Green Rock Worm

Rhyacophila spp. (R. fuscula, R. manistee and others in Michigan)

Also called Rhyacophila, Green Caddis Larva, Free-Living Caddis.

A free-living caddis larva of fast, cold riffles that trout and steelhead eat year-round; it is one of the classic Michigan nymphs rather than a hatch to wait for. The bright green larva builds no case and gets knocked into the drift constantly, so a #12-16 green caddis larva dead-drifted along the bottom works in any month, and West Michigan TU singles out a green Rhyacophila larva as effective for Muskegon steelhead. Fish it as a point fly under an indicator or in a Euro rig, especially in winter and spring when little else is hatching. Adults are not a significant Michigan surface hatch.

#12–16all daylarvabright green to olive-green larvadark head and legsolive-bodied adult with mottled gray-brown wing

Green Rock Worm (Rhyacophila dorsalis), adult — © Josh Boe · CC BY · iNaturalist · Lymm, UK · 2025

© Tina Ellegaard Poulsen · CC BY · iNaturalist · Åkær Å, Danmark · 2025
© Dorte Stokholm · CC BY · iNaturalist · Region Midtjylland, DK · 2023
Todd Folsom · CC0 · iNaturalist · Whatcom County, WA · 2022
© Tommy Andriollo · CC BY · iNaturalist · 1226 Thônex, Suisse · 2023
Josie Monaghan · CC0 · iNaturalist · Skipton BD23 5PS, UK · 2025

Timing by region

Southeast Lower Peninsula
1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D
Window
All year
Peak
—
Southwest Lower Peninsula
1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D
Window
All year
Peak
—
Northeast Lower Peninsula
1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D
Window
All year
Peak
—
Northwest Lower Peninsula
1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D
Window
All year
Peak
—
Upper Peninsula
1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D
Window
All year
Peak
—

Region	Months	Window	Peak
Southeast Lower Peninsula	J F M A M J J A S O N D	All year	—
Southwest Lower Peninsula	J F M A M J J A S O N D	All year	—
Northeast Lower Peninsula	J F M A M J J A S O N D	All year	—
Northwest Lower Peninsula	J F M A M J J A S O N D	All year	—
Upper Peninsula	J F M A M J J A S O N D	All year	—

Flies that match

Reference photo

Green Caddis Larva

Larva / pupa#6–16GreenChartreuseOlive+3

A Michigan steelhead staple: the green Rhyacophila larva is 'effective on the Muskegon River for steelhead' and Current Works lists caddis #6 to #12 among its top five, bright green or chartreuse for stained water and olive or cream naturals for low clear flows. Betts names green caddis larvae with Hex nymphs and eggs on the Pere Marquette flies-only water. Fish it as the trailer behind an egg or stonefly, year-round.

Indicator nymphing · Chuck and duck · Euro / tight-line nymphing

Reserve · $2.75

Bench photo coming

PM Caddis

Larva / pupa#8–12GreenChartreuse

A Pere Marquette caddis larva named by Current Works among its Michigan steelhead caddis (with the Disco Caddis and Boogie Woogie Caddis). Fish it in tandem behind an egg on the PM's flies-only water from fall through the spring spawn.

Indicator nymphing · Chuck and duck

Reserve · $2.75