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Blackfly (Simulium spp.)
Midge, hatching April–June, active in water between 40 and 65°F, and imitated at #18–22. Recorded from northern lower Michigan, southern lower Michigan and the Upper Peninsula, where 1140 Michigan rivers on this site carry a page.
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- #18–22Hook size
- 40–65°FWater, active
- Apr–JunPeak months
- 3Life stages fished
What it is
Midge · Simulium spp. · larva → pupa → adult
Very small and very dark. The larva is a stubby dark cylinder anchored by its rear end to rock in fast water, waving in the current in dense colonies; the adult is the biting blackfly of northern spring.
The larvae anchor in fast shallow riffle in enormous numbers and are torn loose constantly. Nobody fishes a blackfly on purpose; a small black beadhead in a spring riffle is one whether the angler intends it or not.
When it hatches
Peak is April–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 40°F to 65°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.
| Stage | What it is |
|---|---|
| larva | Anchored in the fastest, shallowest riffle in colonies dense enough to darken the stone. Torn loose in numbers by current, which is what puts them in the drift. |
| pupa | Sits in a small cone-shaped case on the rock, then rises to the surface in a bubble of gas and emerges almost instantly. |
| adult | Emerges and leaves quickly. Nobody fishes an adult blackfly; the larva is the stage that matters. |
Matching flies
5 patterns in this book imitate the Blackfly, 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 Beauty nymph · #18–24 — Midge pupa, fished under an indicator in slow winter water.
- Blackfly Larva nymph · #18–22 — A tiny black tapered body on a curved hook. Dropped off something bigger in a spring riffle.
- Brassie nymph · #16–22 — Copper wire and peacock. Sinks fast for its size, which is the point.
- Griffith's Gnat dry fly · #18–24 — A cluster of midges in one fly. The winter dry, and the answer to unexplained sippers.
- Zebra Midge nymph · #18–24 — Two materials and a bead. The winter fly, and the fly for the last two feet of a tailout.
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
- southern lower Michigan MI
- the Upper Peninsula MI
- the Wisconsin driftless WI
- northern Wisconsin WI
- the Virginia mountains VA
- the North Carolina mountains NC
Rivers in these regions with a page here
- Au Sable River
- Muskegon River
- Escanaba River
- Kalamazoo 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
- Apel Drain
- Apple Creek
- Arsenault Creek
- and 1116 more
Related hatches
Same family, or overlapping this one's calendar on the same water.
- Midge Chironomidae · Midge · all year
- Cranefly Tipula spp. · Other · April–June and September–October
- Green Rock Worm / Green Weenie Rhyacophila spp. · Caddis · April–June and September–October
- Blue-Winged Olive Baetis spp. · Mayfly · March–May and September–November
- Caterpillar Lepidoptera larvae · Terrestrial · May–September