Gray Drake (Siphlonurus spp.)

Mayfly, hatching June–July, active in water between 55 and 68°F, and imitated at #10–12. Recorded from 3 of the 8 regions this map covers, across Michigan and Wisconsin.

A large grey-bodied mayfly whose hatch is really an evening spinner fall, peaking in June and July on water running 55 to 68 degrees — a band that spans cold, cold-transitional and cool streams. The nymph is the oddity: not a burrower but a fast, minnow-like swimmer in weedy slow water, best swum rather than dead-drifted. In most places it crawls out onto the bank to emerge, which is why anglers watching for duns on the surface see almost none, and why the dun is barely fishable at all. What matters comes at dusk, when enormous falls of grey spent-wing spinners settle over the same flats night after night for two or three weeks. Hook sizes are 10 and 12. A Gray Drake Spinner at 10 to 12 is the direct answer; an Adams or Parachute Adams, 12 to 20, covers the rest. The records here span northern and southern lower Michigan and northern Wisconsin, and say nothing about which particular flats hold it.

#10–12Hook size
55–68°FWater, active
Jun–JulPeak months
3Life stages fished

Subbasins with trout water where it is on record: 53 of 326 across the 6 states this map draws.

See the trout water on the live map → Every reach coloured by water temperature — the water these hatches come off.

What it is

Mayfly · Siphlonurus spp. · nymph → dun → spinner

A large grey-bodied mayfly whose nymph is a strong swimmer rather than a burrower. The dun is rarely seen on the water; the spinner fall is the event.

The nymph crawls out to emerge, so the dun is barely fishable. The evening spinner fall is the whole hatch.

When it hatches

Peak is June–July. 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.

JFMAMJJASOND

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.

55°F 68°F

Active from 55°F to 68°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
nymph	A fast, minnow-like swimmer in weedy slow water. Swum, not dead-drifted.
dun	Emerges by crawling out on the bank in most places, which is why anglers who watch for duns on the water see almost none.
spinner	Enormous evening falls of grey spent-wing spinners over the same flats, night after night, for two or three weeks.

Matching flies

3 patterns in this book imitate the Gray Drake, 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.

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.

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
northern Wisconsin WI

Rivers in these regions with a page here

Related hatches

Same family, or overlapping this one's calendar on the same water.

Open the trout map →Every trout stream near you, coloured by today's water temperature.