Mahogany Dun (Paraleptophlebia spp.)

Mayfly, hatching September–October, active in water between 45 and 58°F, and imitated at #16–18. Recorded from the Wisconsin driftless, where 364 Wisconsin rivers on this site carry a page.

An autumn mayfly, size 16 to 18, dark reddish-brown, arriving in September and October when almost everything else has finished. Two tails, slate wings, and a body the colour its name says. The nymph is a slender crawler in slower water and leaf litter. Emergence is slow and film-bound, in the middle of the day, on falling water temperatures, and the dun rides low on cold water; the spinner falls in the evening with a dark rusty body. The active band is 45 to 58 degrees, covering cold and cold-transitional water, with the peak in September and October. It overlaps the fall Olives and is a size larger, which is often the difference on a refusing fish. A Blue Quill in 16 to 18 or a Parachute Adams in 12 to 20 covers the dun, an RS2 in 16 to 24 the film, and a Pheasant Tail in 12 to 22 the nymph.

#16–18Hook size
45–58°FWater, active
Sep–OctPeak months
4Life stages fished

Subbasins with trout water where it is on record: 7 of Wisconsin's 43.

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

What it is

Mayfly · Paraleptophlebia spp. · nymph → emerger → dun → spinner

A dark reddish-brown mayfly, size 16 to 18, that arrives in September and October when almost everything else has finished. Two tails, slate wings, and a body the colour its name says.

Autumn. Overlaps the fall Olives and is a size larger, which is often the difference on a refusing fish.

When it hatches

Peak is September–October. 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.

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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.

45°F 58°F

Active from 45°F to 58°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	A slender crawler in slower water and leaf litter.
emerger	Autumn emergences are slow and film-bound, in the middle of the day, on falling water temperatures.
dun	Dark mahogany body, riding low on cold water.
spinner	Evening fall, dark rusty body.

Matching flies

4 patterns in this book imitate the Mahogany Dun, 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
the Upper Peninsula MI
the Wisconsin driftless WI
the Virginia mountains VA
the North Carolina mountains NC

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.