Michigan Flies

Hatches / stonefly

Giant Black Stonefly

A

Pteronarcys dorsata

Also called Giant Stonefly, Salmonfly (eastern), Pteronarcys, Giant Stone.

The largest Michigan stonefly, up to two inches, widespread in the state but mostly nocturnal, so it is generally fished as a nymph rather than a hatch. On the Pine River, the coldest, fastest river in the Lower Peninsula, Pteronarcys nymphs #2-6 are the staple food and the best big-rainbow fly; on the Au Sable, guides note stoneflies producing quality trout in early May. Emergence is sporadic and after dark from mid-May through June, when a big dark adult fished after dark on the Muskegon or Manistee can move a large brown. Dead-drift a heavy #4-6 black stonefly nymph along the bottom of fast runs any month of the year.

#2–8nightdusknymphadultdark brown to black bodydark smoky wing (up to 2 inches)dark brown nymph with orange at the leg joints

Phillip Hogan · CC0 · iNaturalist · Ishpeming Township, MI · 2023

Timing by region

  1. 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
    May 1 – Jun 16
    Peak
    —
  2. 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
    May 5 – Jun 20
    Peak
    —
  3. 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
    May 15 – Jun 30
    Peak
    —
  4. 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
    May 15 – Jun 30
    Peak
    —
  5. 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
    Jun 5 – Jul 21
    Peak
    —

Flies that match

Pat's Rubber Legs (reference photo)Reference photo
Pat's Rubber Legs
A
Nymph#4–10BlackBrownCoffee-black+1

A U.P. steelhead guide's nymph rig runs double-bead stoneflies and Pat's Rubber Legs #8 to #10 in black and brown as the point fly ahead of an egg or caddis. For trout it is a generic big stonefly for the Pine, Upper Manistee and Sturgeon, fished deep in fast water year-round; Michigan trout sources do not name it, so treat the trout use as generic.

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

Reserve · $2.75
20 Incher (reference photo)Reference photo
20 Incher
A
Nymph#6–12Peacock and brown with goose biots

Current Works lists the 20 Incher among its Michigan steelhead stoneflies #6 to #12, alongside Ted's Early Black Stone and Mercer's Biot Epoxy Stone. It doubles as a golden stone nymph for trout from mid May through August, fished tight to the banks where Acroneuria nymphs migrate before crawling out.

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

Reserve · $2.75
Giant Black Stonefly Nymph (Pteronarcys) (reference photo)Reference photo
Giant Black Stonefly Nymph (Pteronarcys)
A
Nymph#2–8Black-brown

Pteronarcys dorsata nymphs live two to four years, so the #2 to #6 nymph is available all year and is the Pine River staple, where Hawkins calls it a river of nymphs, sculpins and baitfish rather than a surface river. Bounce it through fast pockets on the Pine, Sturgeon and Upper Manistee; the adults emerge sporadically at night from mid May to June and are rarely fished.

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

Reserve · $2.75