Mahogany Dun

Paraleptophlebia · genus

A small, dark mayfly that can bring selective trout to the surface when duns and spinners gather.

Overview

About Mahogany Dun

Mahogany Dun is the angler name commonly applied to mayflies in the genus Paraleptophlebia, a group in the family Leptophlebiidae. This genus is found in North America and parts of Western Europe, and anglers watch for its nymphs, emergers, duns, and spinners when trout key on smaller mayflies.

Life Cycle

Eggs

Female mayflies deposit hundreds to thousands of eggs either directly in or near the water. These eggs then sink and attach to the stream bottom.

nymph

Mayfly nymphs reside on the stream bed, continuously feeding and growing through several molting phases before transforming.

emerger

The nymph ascends from the bottom to the water's surface, where it undergoes its final molt, hatching into the adult stage.

dun

The freshly emerged adult, known as a dun, typically rests on the water's surface or on nearby vegetation as its wings dry and harden.

spinner

After a final molt, the dun transforms into a sexually mature spinner. These mated adults rise into the air in swarms to mate.

Egg-Laying Spinner

Once mating is complete, the female spinner returns to the water's surface to deposit her eggs, starting the cycle anew.

Spent Spinner

Following egg-laying, the adult mayfly dies. Spent spinners are often found floating lifelessly on the water's surface, a significant food source for fish.

Stages: Anglers commonly imitate the nymph, emerger, dun, and spinner stages. As a mayfly genus, Paraleptophlebia follows the typical mayfly pattern of aquatic nymphs developing in the water before emerging to winged adults and later returning as spent spinners.
Emergence cues: Look for activity in cooler shoulder-season conditions or during periods when small dark mayflies begin showing on the surface, often with the best emergence during calmer parts of the day.
Behavior: Nymphs drift naturally before emergence, emergers can hang in or just below the surface film, duns ride the water briefly after hatching, and spinners fall spent and flat to the surface.

Where It Hatches

Mahogany Dun

One species, multiple rivers.

River

Fly Patterns

Mahogany Dun#16-18

Angler Notes

Why it matters: Mahogany Duns matter because trout can become highly selective to these small dark mayflies, especially when fish shift from general feeding to surface-focused feeding on emergers, duns, or spent adults.
Imitation tips: Carry slim dark nymphs, low-riding emergers, sparse upright-wing duns, and flush spinners in understated brown, mahogany, and gray tones. Keep patterns trim rather than bushy.
Key life stages: nymphemergerdunspinner
Presentation: Fish nymphs on a dead drift near likely holding seams, then switch to emerger or dun patterns when you see rises. For spinner falls, use a drag-free presentation and let the fly sit low and flat in the film.

Identification

Key features: Slim mayfly profile with an upright-winged dun stage and a delicate, long-tailed look; anglers usually notice them as small, darker-bodied mayflies compared to brighter pale mayflies.
Size: Small; typically fished in the small mayfly range.
Coloration: Usually dark brown to mahogany-toned bodies with subdued gray to smoky wings; nymphs are generally darker and mottled.
Similar bugs: Blue-winged OlivePale Morning Dunsmall mayflies

Habitat

Water types: riversstreamsspring creeksstillwaters
Substrate: Common around weedbeds, soft seams, and mixed bottoms with organic material, though nymphs may also occur among rocks and aquatic vegetation.
Conditions: Most important to anglers in cooler, moderately clean water where mayfly nymphs can develop and surface activity is easy for trout to target.