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Alderfly (Sialis spp.)
Other, hatching May–June, active in water between 52 and 66°F, and imitated at #10–14. Recorded from the Virginia mountains, where 796 Virginia rivers on this site carry a page.
- #10–14Hook size
- 52–66°FWater, active
- May–JunPeak months
- 2Life stages fished
What it is
Other · Sialis spp. · larva → adult
A dark, sturdy fly with hard, heavily veined brown-black wings folded like a roof, and no tails. It flies badly and lands worse.
A dark, hard-winged fly of shaded alder-lined water in late spring. The adult is a poor flier and lands on the water badly, which is most of the reason trout bother with it.
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 52°F to 66°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 | A predatory larva in silt and detritus in slower water, with fringed lateral filaments and a single tapering tail. It crawls out onto the bank to pupate rather than emerging on the water. |
| adult | On the water in late spring where the banks are alder-lined and shaded. It is a poor flier, so it arrives by falling, and a dark wet fly fished just under the film is the traditional and correct answer. |
Matching flies
4 patterns in this book imitate the Alderfly, 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.
- Alder Fly wet fly · #10–14 — Dark peacock body, mottled hen wing. An old British wet fly that happens to match Sialis exactly.
- Black Stonefly Nymph nymph · #12–18 — Dead-drifted along the bottom. Stonefly nymphs are always present in rocky water.
- Hare's Ear Nymph nymph · #10–18 — Looks like everything and nothing. The other half of a two-nymph rig.
- Partridge & Orange Soft Hackle wet fly · #12–18 — Swung down and across. The simplest fly here and among the most effective.
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.
- Cascades Creek the Virginia mountains · July mean 59.2°F
- Left Prong Wilson Creek the Virginia mountains · July mean 59.2°F
- Lick Block Run the Virginia mountains · July mean 59.2°F
- Camp Branch the Virginia mountains · July mean 56.0°F
- Falling Spring Creek the Virginia mountains · July mean 63.1°F
- Indiandraft Creek the Virginia mountains · July mean 63.1°F
- Jerrys Run the Virginia mountains · July mean 63.1°F
- Als Run the Virginia mountains
- Alum Creek the Virginia mountains
- Anderson Run the Virginia mountains
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
- the North Carolina mountains NC
Rivers in these regions with a page here
- Jackson River
- Smith River
- Als Run
- Alum Creek
- Amos Branch
- Anderson Run
- Ararat River
- Auberry Creek
- Back Creek
- Back Creek
- Back Fork
- Back Run
- Baker Branch
- Baldwin Branch
- Baldwin Branch
- Barbours Creek
- Bark Camp Branch
- Bark Camp Branch
- Barkcamp Branch
- Barnard Creek
- Barney Run
- Barterbrook Branch
- Batie Creek
- Battery Creek
- and 772 more
Related hatches
Same family, or overlapping this one's calendar on the same water.
- Cranefly Tipula spp. · Other · April–June and September–October
- Aquatic Worm Oligochaeta · Other · all year
- Damselfly Zygoptera · Other · all year
- Dragonfly Anisoptera · Other · all year
- Leech Hirudinea · Other · all year