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Giant Black Stonefly (Salmonfly) (Pteronarcys dorsata)
Stonefly, hatching May–June, active in water between 50 and 62°F, and imitated at #4–6. Recorded from northern lower Michigan and the Upper Peninsula, where 985 Michigan rivers on this site carry a page.
The largest insect in these rivers: a stonefly nymph two inches long, glossy black-brown, with two tails and two hooked claws on each leg. Its life cycle runs multiple years, so the nymph is in the river every day of every year, crawling among cobble and woody debris and being dislodged constantly — which makes a big black rubber-legged nymph a searching fly wherever they live. Hooks for the insect itself run size 4 to 6, the active band is 50 to 62 degrees, and the peak is May and June in cold and cold-transitional water. The adult crawls to the bank to hatch rather than emerging in open water, so the emergence happens at night and is easy to miss entirely, and the nymph matters more than the dry. Adults return at dusk to lay eggs. Pat's Rubber Legs in 4 to 10 or a black Woolly Bugger in 2 to 12 covers the sunk stage.
- #4–6Hook size
- 50–62°FWater, active
- May–JunPeak months
- 2Life stages fished
What it is
Stonefly · Pteronarcys dorsata · nymph → adult
The largest insect in these rivers — a stonefly nymph two inches long, glossy black-brown, with two tails and two hooked claws on each leg. Multi-year life cycle, so the nymph is in the river every day of every year.
The eastern cousin of the western salmonfly. The emergence is at night and easy to miss; the nymph is a year-round meal.
When it hatches
Peak is May–June. 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.
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.
Active from 50°F to 62°F. On this map that is cold, cold-transitional water — the band crosses 1 of the three break 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.
| Stage | What it is |
|---|---|
| nymph | Crawls among cobble and woody debris. Dislodged constantly, and a big black rubber-legged nymph is a searching fly on any river that holds them. |
| adult | Crawls to the bank to hatch rather than emerging in open water, which is why the nymph matters more than the dry. Adults return to lay eggs at dusk. |
Matching flies
4 patterns in this book imitate the Giant Black Stonefly (Salmonfly), 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.
- Black Stonefly Nymph nymph · #12–18 — Dead-drifted along the bottom. Stonefly nymphs are always present in rocky water.
- Chubby Chernobyl dry fly · #8–14 — Foam attractor and indicator in one. Hopper-dropper season starts here.
- Pat's Rubber Legs nymph · #4–10 — Ugly, heavy, and the single best searching nymph in high or coloured water.
- Woolly Bugger (Black) streamer · #2–12 — If you could only own one fly. Leech, sculpin, big nymph, all of it.
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.
- Baldwin River northern lower Michigan · July mean 61.3°F
- Beaver Creek northern lower Michigan · July mean 61.3°F
- Bray Creek northern lower Michigan · July mean 61.3°F
- Coe Creek northern lower Michigan · July mean 61.3°F
- Diamond Lake Outlet Creek northern lower Michigan · July mean 61.3°F
- East Branch Hersey Creek northern lower Michigan · July mean 61.3°F
- East Branch Pine River northern lower Michigan · July mean 61.3°F
- Hersey Creek northern lower Michigan · July mean 61.3°F
- Hoxey Creek northern lower Michigan · July mean 61.3°F
- Johnson Creek northern lower Michigan · July mean 61.3°F
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.
- northern lower Michigan MI
- the Upper Peninsula MI
- northern Wisconsin WI
- the Virginia mountains VA
- southeast Minnesota MN
Rivers in these regions with a page here
- Au Sable River
- Muskegon River
- Escanaba River
- Abitosse Creek
- Acme Creek
- Adams Creek
- Addis Creek
- Adventure Creek
- Aho Creek
- Ahola Creek
- Alabaster Whitney Drain
- Aldridge Creek
- Allen Creek
- Alward Creek
- Amundsan Creek
- Anderson Bayou
- Anderson Creek
- Anna River
- Antler Creek
- Antrim Creek
- Apple Creek
- Arsenault Creek
- Asum Creek
- Atkinson Creek
- and 961 more
Related hatches
Same family, or overlapping this one's calendar on the same water.
- Golden Stonefly Acroneuria spp. · Stonefly · June–July
- Little Yellow Sally Isoperla spp. · Stonefly · June–August
- Little Brown Stonefly Taeniopteryx / Strophopteryx spp. · Stonefly · February–April
- Little Black Stonefly Allocapnia / Capnia spp. · Stonefly · January–April
- Cranefly Tipula spp. · Other · April–June and September–October