The Mayfly Lifecycle: Patterns, Techniques, and Best Practices for Colorado Fly Fishing

The mayfly is one of the most iconic aquatic insects in the world of fly fishing. Renowned for its delicate, ephemeral beauty and critical role in trout diets, the mayfly serves as a primary focus for anglers seeking success on rivers, streams, and stillwaters. Understanding the lifecycle of mayflies, the patterns that imitate them, and the best techniques for each stage can make all the difference, especially in Colorado’s diverse waters.

This article will provide an in-depth look at the mayfly lifecycle, the best times and places to fish for them, and how to use fly patterns to maximize your success.

The Mayfly Lifecycle

Mayflies undergo a complete metamorphosis, which includes four main stages: egg, nymph, emerger, and adult. Each stage presents unique opportunities for fly anglers, as trout feed selectively depending on environmental conditions and the mayfly’s stage.

1. Egg Stage

• Description:

Female mayflies deposit their eggs on the water’s surface or directly under it, often during their dramatic death spirals. The eggs sink to the substrate, where they incubate and eventually hatch into nymphs.

• Fly Fishing Relevance:

While not directly targeted by anglers, understanding the egg-laying habits of adult mayflies can help you locate areas where future nymph hatches will concentrate trout.

2. Nymph Stage

• Description:

Once hatched, mayfly nymphs live for months to years in the substrate. These nymphs are active swimmers or clingers, depending on the species. In Colorado, mayfly nymphs like the Blue-Winged Olive (Baetis) and Pale Morning Dun (PMD) are common.

• Behavior:

• Drift in the current occasionally (behavioral drift).

• Cling to rocks or aquatic vegetation in freestones and tailwaters.

• Patterns to Imitate Nymphs:

• Pheasant Tail Nymph: A versatile pattern for Baetis and PMDs.

• Two-Bit Hooker: A heavier pattern that sinks quickly in fast currents.

• RS2 (Nymph Version): A great option for small, active nymphs.

• Best Times to Fish Nymphs:

Year-round, especially before hatches. Baetis nymphs are particularly active in spring and fall.

• Best Technique:

Use dead-drift nymphing techniques with an indicator rig or Euro-nymphing setup. Target riffles and runs where nymphs are dislodged from the substrate.

• Best Places to Fish Nymphs:

• Tailwaters: South Platte River, Fryingpan River.

• Freestones: Roaring Fork, Cache la Poudre.

3. Emerger Stage

• Description:

As nymphs mature, they transition into emergers, ascending through the water column to hatch into adults. This stage is highly vulnerable to predation.

• Behavior:

Emergers pause just below the surface as they shed their exoskeleton, making them easy targets for trout.

• Patterns to Imitate Emergers:

• RS2 (Emerger Version): Perfect for imitating emerging Baetis and PMDs.

• Barr’s Emerger: A deadly pattern for technical trout.

• Sparkle Dun: A versatile pattern with a trailing shuck to mimic emerging insects.

• Best Times to Fish Emergers:

Just before and during hatches in spring, summer, and fall.

• Best Technique:

Use dry-dropper rigs with an emerger trailing behind a dry fly. Alternatively, swing emergers through riffles.

• Best Places to Fish Emergers:

• Tailwaters: Cheesman Canyon, Fryingpan River.

• Stillwaters: Spinney Mountain Reservoir.

4. Adult Stage

• Description:

Adult mayflies fall into two categories: duns (freshly emerged adults) and spinners (mature adults returning to lay eggs).

• Behavior:

• Duns rest on the surface to dry their wings, creating perfect targets for trout.

• Spinners perform mating dances and often fall spent onto the water.

• Patterns to Imitate Adults:

• Parachute Adams: A classic pattern for Baetis and PMDs.

• Extended Body PMD: Imitates Pale Morning Duns perfectly.

• Rusty Spinner: A must-have for imitating spent spinners.

• Best Times to Fish Adults:

• Duns: Midday during active hatches.

• Spinners: Evenings or early mornings during spinner falls.

• Best Technique:

Dead-drift dry flies along seams and in slower pools. Look for rising trout and cast ahead of their feeding lanes.

• Best Places to Fish Adults:

• Tailwaters: Fryingpan River (notorious for its PMD hatches).

• Small Streams: Rocky Mountain National Park.

Best Times to Fish Mayflies in Colorado

Colorado’s diverse waters offer year-round opportunities to fish mayflies, though certain times of year are better for specific species:

1. Spring (March–May):

• Species: Blue-Winged Olive (Baetis).

• Best Times: Overcast days in late morning to early afternoon.

• Best Waters: Tailwaters like Cheesman Canyon and Eleven Mile Canyon.

2. Summer (June–August):

• Species: Pale Morning Dun (PMD), Green Drake.

• Best Times: Late mornings and evenings.

• Best Waters: Freestones like the Roaring Fork and Colorado River.

3. Fall (September–October):

• Species: Blue-Winged Olive (Baetis), Tricos.

• Best Times: Mid-morning for Trico spinner falls; overcast afternoons for Baetis.

• Best Waters: Tailwaters and small spring creeks.

4. Winter (November–February):

• Species: Blue-Winged Olive (Baetis).

• Best Times: Midday during warm spells.

• Best Waters: Tailwaters like the Fryingpan River.

Best Places to Fish Each Stage of the Lifecycle

Eggs:

• Focus on runs and riffles where females lay eggs. While you don’t fish eggs directly, these areas are hotspots for future activity.

Nymphs:

• Fish near the substrate in riffles, runs, and pocket water. Use Euro-nymphing or indicator rigs to get your flies down.

Emergers:

• Target the water column in slow seams, back eddies, and just below riffles. Watch for subtle rises indicating trout feeding subsurface.

Adults (Duns and Spinners):

• Look for rising trout in slower pools and near seams during hatches. Spinner falls often concentrate in flat, glassy water.

Techniques for Fishing Mayfly Patterns

1. Dead-Drift Nymphing:

• Essential for nymph and emerger stages. Ensure your flies drift naturally without drag.

• Use an indicator or tight-line nymphing setup for control.

2. Dry-Dropper Rigs:

• Combine a high-floating dry fly with an emerger or nymph dropper. This setup covers multiple water column levels.

3. Swinging Emergers:

• Cast across and downstream, allowing emergers to rise naturally at the end of the swing.

4. Dry Fly Fishing:

• Focus on precise presentations and dead drifts. Pay attention to drag-free drifts in slower water.

5. Spinner Fishing:

• Use spinner patterns during evening falls. Cast to trout feeding on spent mayflies.

Colorado-Specific Tips

• Adjust to Elevation:

At higher elevations, hatches often occur later in the day due to cooler temperatures.

• Focus on Tailwaters:

Tailwaters like Cheesman Canyon, Fryingpan River, and Blue River provide consistent flows and temperatures, making them ideal for year-round mayfly activity.

• Be Ready for Wind:

In freestone rivers, windy afternoons can disrupt surface hatches but often concentrate spinners in calm eddies.

Conclusion

Mayflies are an essential part of Colorado’s fly fishing landscape, offering year-round opportunities to target trout. By understanding their lifecycle, carrying the right patterns, and tailoring your techniques to each stage, you can maximize your success on Colorado’s iconic waters. Whether you’re fishing Baetis in Cheesman Canyon or chasing PMDs on the Fryingpan, mayflies provide endless opportunities to connect with the water and the trout that call it home.

“-Until next time—fly fish your water, your way.”

JRO