Mayfly Fly Fishing: Hatches, Patterns & Life Cycle Guide

Description

Mayflies (Order Ephemeroptera) are the quintessential insect of fly fishing. When an angler pictures "matching the hatch" with a dry fly, they are almost always visualizing a mayfly. Elegant, fragile, and universally available in clean trout waters, these insects drive the most famous feeding frenzies in the sport. There are over 3,000 species worldwide, ranging from the massive Hexagenia (#4) to the microscopic Trico (#26). All share the same defining characteristics: an aquatic nymphal stage, upright sailboat-like wings in the adult (Dun) stage, and a unique final reproductive stage (Spinner).

Life Cycle Stages

Nymph

Mayflies spend 99% of their life underwater as nymphs. They generally fit into four behavioral groups: Clingers (e.g., March Browns): Flat bodies, live in fast rocky water. Crawlers (e.g., PMDs, BWOs): Stocky bodies, live in riffles and runs. Swimmers (e.g., Callibaetis, Drakes): Streamlined minnow-like bodies, live in slower water. Burrowers (e.g., Hexagenia): Tusks and shovel legs, live in silt/muck. Fishing Tactic: Dead-drift pheasant tails or hare's ear nymphs near the bottom.

Recommended Fly Patterns

Mercer's Green Drake Poxyback

#10-#12

Olive

Blow Torch

#14-#18

Olive, Brown, Black

Copper John

#14-#20

Copper, Red, Green, Black

Pheasant Tail Nymph

#14-#20

Brown, Copper, Olive

Lightning Bug

#16-#20

Pearl, Silver, Olive

Hare's Ear Nymph

#12-#18

Natural, Olive, Tan

Two Bit Hooker PMD

#14-#18

Pale Yellow, Sulphur, Olive, Brown

Micro May PMD

#14-#18

Pale Yellow, Sulphur, Olive, Brown

Red Dart

#12-#18

Red, Purple, Blue, Black

Slim Shady

#18-#24

Olive, Brown

Perdigon

#14-#20

Olive, Dark Olive, TB, Brown, Black, Purple, Pink, Butano, Copper

Prince Nymph

#12-#18

Peacock, Brown, White, Gold

Juju Baetis

#18-#22

Olive, Brown, Gray

Duracell

#14-#18

Brown, Black

Hare's Ear Jig

#10-#18

Natural, Olive, Brown, Black

Spanish Bullet Perdigon

#14-#18

Olive, Brown, Copper, Black

Pheasant Tail Jig

#12-#18

Natural, Copper, Chartreuse Hot Spot, Pink Hot Spot

Frenchie

#14-#18

Brown, Olive

Split Case PMD

#14-#18

Pale Yellow, Sulphur, Olive, Brown

Juju PMD

#14-#20

Pale Yellow, Sulphur, Olive, Tan, Silver

Psycho Prince

#12-#18

Orange Belly, Purple, Dirty Pink, Caddis Green, Blue, Black

Rojo Midge

#18-#22

Red, Black, Silver, White

Black Beauty

#20-#24

Black

Top Secret Midge

#20-#24

Brown, Black, Gray, White

Zebra Midge

#18-#22

Black, Red, Olive, Cream

Brassie

#18-#22

Copper, Olive, Black

Emerger

During the hatch, the nymph swims to the surface or crawls to a rock. The transformation from aquatic nymph to aerial adult happens in the surface film. This is the most vulnerable moment in the life cycle. The insect is often stuck in its shuck, unable to fly or swim effectively. Fishing Tactic: Fish a floating nymph (RS2, WD40) in the surface film or just below it.

Recommended Fly Patterns

Sparkle Dun

#14-#22

Pale Yellow, Olive, Tan, Gray, Brown, Green

RS2

#16-#22

Gray, Olive, Black

Barr's Emerger

#16-#24

Olive, Pale Yellow, Gray, Tan, Brown

Film Critic

#10-#16

Olive, Gray, Brown

Klinkhammer Special

#12-#18

Tan, Olive, Peacock, Black

Soft Hackle Hare's Ear

#12-#16

Natural, Olive, Orange

WD-40

#18-#22

Gray, Olive, Brown, Black

Rojo Midge

#18-#22

Red, Black, Silver, White

Black Beauty

#20-#24

Black

Top Secret Midge

#20-#24

Brown, Black, Gray, White

Dun (Subimago)

This is the classic "dry fly" stage. The adult mayfly has opaque, dull-colored wings (often gray, olive, or dun) that stand upright like a sailboat. They must float on the water to dry their wings before flying to streamside vegetation. Fishing Tactic: Cast a Parachute Adams, Sparkle Dun, or Thorax Dun to rising fish.

Recommended Fly Patterns

PMD Comparadun

#14-#18

Yellow, Tan

Green Drake Comparadun

#10-#14

Olive, Gray, Brown

BWO Comparadun

#16-#20

Olive, Gray

Rusty Spinner

#16-#20

Rust, Brown, Tan, Orange

Royal Wulff

#10-#18

Brown, Red, White

Last Chance Cripple (BWO)

#18-#22

Olive, Gray

Purple Haze

#14-#20

Purple, Gray

Last Chance Cripple (PMD)

#16-#18

Yellow, Tan

Parachute Adams

#12-#20

Gray, Brown

Trico Dun

#20-#24

Black, Gray, Olive

Parachute BWO

#16-#22

Olive, Gray

PMD Spinner

#14-#20

Tan, Olive, Yellow, Gray

Trico Spinner

#18-#24

Black, Gray, White

Green Drake Cripple

#10-#12

Olive

Parachute PMD

#14-#18

PMD Tan, Olive, Yellow

Parachute Drake

#10-#14

Olive, Gray, Brown, Tan

Green Drake Hairwing

#10-#12

Olive, Brown, Gray, Cream

Parachute Mahogany Dun

#16-#20

Reddish Brown, Rust, Dark Dun, White Post

Griffith's Gnat

#18-#22

Black, Gray

Habitat

Mayflies are undeniably linked to Clean Water. Their presence is a primary indicator of a healthy river ecosystem. While specific species prefer different micro-habitats (burrowing in silt, clinging to rocks in fast riffles, or swimming in weeds), the order as a whole requires cold, oxygenated, unpolluted water. They are found in freestone rivers, tailwaters, spring creeks, and stillwaters across the globe.

Behavior

Mayfly hatches are often triggered by water temperature or light conditions. Cloud cover is a massive catalyst; "bad weather" days (drizzle, overcast) often produce the best Blue-Winged Olive (BWO) hatches because the high humidity prevents the duns' wings from drying quickly, keeping them on the water longer for trout to eat.

Fishing Information

Matching the Hatch Complexity varies, but anglers generally need to match three things:

Size: The most distinct variable. A #12 Green Drake looks nothing like a #20 BWO to a trout.
Silhouette: Is the fish eating the dun (high profile) or the emerger/spinner (low profile/flush)?
Color: General shades match well (Olive, Yellow/Pale, Brown, Gray).

Major Hatches (Calendar)

Winter/Spring: Midges (technically Diptera but fished similarly), Early BWOs.
Spring: March Browns, Blue-Winged Olives, Skwalas (Stonefly).
Summer: Pale Morning Duns (PMD), Green Drakes, Sulfurs, Yellow Sallies (Stonefly), Tricos.
Fall: Tricos, Mahogany Duns, Late BWOs, October Caddis.

Conservation Status

Mayflies are the classic "canary in the coal mine." Their disappearance from a watershed is an early warning sign of pollution, sedimentation, or thermal degradation. Conservation of cold-water fisheries is synonymous with the conservation of mayflies.