What hatches in September: flies and patterns

9 entries in the Hatch Window curated chart are typically active in September, with the fly patterns that match each.

By water type

• Tailwater: Midges, Blue-Winged Olive, Trico, Hoppers, ants & beetles, Sulphur, Scuds & Sowbugs, White Fly, Mahogany Dun
• Freestone: Midges, Blue-Winged Olive, Hoppers, ants & beetles, Sulphur, Isonychia / Slate Drake, White Fly, Mahogany Dun
• Spring creek: Midges, Blue-Winged Olive, Trico, Hoppers, ants & beetles, Sulphur, Scuds & Sowbugs

Hatches and matching patterns

Midges

• Zebra Midge (nymph, size 18-22)
• Griffith's Gnat (dry, size 18-22)
• Rojo Midge (nymph, size 20-24)

Year-round on tailwaters, most reliable hatch on cold winter days when little else is moving.

Blue-Winged Olive

• Parachute Adams (dry, size 16-20)
• Pheasant Tail Nymph (nymph, size 16-20)
• CDC BWO Sparkle Dun (emerger, size 18-20)

Best on overcast, drizzly spring and fall days; spring and fall are two distinct emergence windows.

Trico

• Trico Spinner (dry, size 20-24)
• CDC Trico Dun (dry, size 20-24)

Early-morning spinner falls; tiny flies and light tippet, technically demanding but very reliable on Western tailwaters and Eastern/Midwest spring creeks alike.

Hoppers, ants & beetles

• Dave's Hopper (terrestrial, size 6-10)
• Chernobyl Ant (terrestrial, size 8-12)
• Foam Beetle (terrestrial, size 12-16)

Late-summer bank-water staple, especially on windy afternoons.

Sulphur

• Sulphur Comparadun (dry, size 16-18)
• Sulphur Dun (dry, size 16-18)
• Sulphur Pheasant Tail (nymph, size 16-18)

A reliable evening hatch on Eastern freestones and Midwest spring creeks alike; a smaller fall emergence follows the main late-spring one.

Isonychia / Slate Drake

• Isonychia Nymph (nymph, size 10-12)
• Slate Drake Dry (dry, size 12-14)
• Adams (dry, size 12-14)

A strong-swimming nymph often fished in the margins during high water; the dun hatch runs through late summer into early fall.

Scuds & Sowbugs

• Scud (olive/tan) (nymph, size 14-18)
• Sowbug (nymph, size 14-18)

Not a hatch, a year-round staple on cold, stable tailwaters and spring creeks (the South Holston and Clinch in Tennessee, the Bighorn and San Juan out West, Pennsylvania limestoners, the Driftless Area) where crustaceans outnumber insects.

White Fly

• White Wulff (dry, size 12-14)
• White Fly Comparadun (dry, size 12-14)
• White Fly Nymph (nymph, size 12-14)

A dense late-summer dusk emergence on Eastern and Midwest rivers (the Yellow Breeches and lower Susquehanna, White River drainages); duns and spinners come off together in a brief, blizzard-like window.

Mahogany Dun

• Mahogany Dun Parachute (dry, size 16-18)
• Pheasant Tail Nymph (nymph, size 16-18)

A reliable fall mayfly, especially on Western tailwaters (the Missouri and Bighorn) on cool, overcast autumn afternoons; a dark reddish-brown dun that follows the late-season BWOs.

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