Pennsylvania Fly Hatches: A Comprehensive Guide for Anglers
Pennsylvania’s rivers, streams, and spring creeks are legendary among fly fishers, boasting some of the most diverse and prolific insect hatches in the eastern United States.
From the misty mornings of early spring to the crisp days of late fall, the Keystone State’s waters come alive with mayflies, caddisflies, stoneflies, and terrestrials.
To fully appreciate Pennsylvania’s fly fishing opportunities, anglers must understand the state’s seasonal hatches, their habitats, and the strategies to match them.
Below, we dive deep into Pennsylvania’s major fly hatches, including lesser-known gems and regional variations.
The Science of Hatches
Aquatic insects follow predictable life cycles tied to water temperature, light, and seasonality.
Trout key in on these emergences, feeding selectively on specific stages: nymphs, emergers, duns (adults), and spinners (egg-laying adults).
Success depends on observing insect behavior, water conditions, and trout feeding patterns.
Pennsylvania’s hatches are influenced by its mix of limestone spring creeks (e.g., Penns Creek, Falling Springs), freestone rivers (e.g., Youghiogheny, Loyalsock), and tailwaters (e.g., Delaware River), each hosting unique insect communities.
Pennsylvania’s Major Hatches by Season
Early Spring (March–April)
Quill Gordon (Epeorus pleuralis)
- Timing: Mid-March to early April
- Habitat: Freestone streams with rocky bottoms.
- Key Rivers: Allegheny River, Slate Run.
- Patterns: Quill Gordon Dry Fly, Pheasant Tail Nymph (size 14–16).
- Tips: Look for cloudy days with water temps above 45°F. Fish nymphs deep in riffles before switching to duns in slower pools.
Blue-Winged Olives (BWOs) (Baetis spp.)
- Timing: February–April (and again in fall).
- Habitat: Cold, oxygenated water; common in tailwaters.
- Patterns: Parachute BWO, RS2 Emerger (size 18–22).
- Tips: Overcast days trigger surface activity. Focus on slow eddies and foam lines.
Little Black Caddis (Chimarra spp.)
- Timing: March–April.
- Habitat: Fast-flowing riffles.
- Patterns: Elk Hair Caddis (black, size 16–18), Zebra Midge.
- Tips: Fish skittering dry flies or swing soft-hackle pupae.
Spring (May–June)
Hendrickson (Ephemerella subvaria)
- Timing: Mid-April to mid-May.
- Habitat: Freestone and limestone streams.
- Key Rivers: Spring Creek, Little Juniata.
- Patterns: Hendrickson Comparadun, CDC Emerger (size 12–14).
- Tips: The spinner fall at dusk is legendary. Use a Rusty Spinner pattern.
March Brown (Maccaffertium vicarium)
- Timing: May–early June.
- Habitat: Riffle-heavy streams.
- Patterns: March Brown Dry, Hare’s Ear Nymph (size 10–12).
- Tips: These mayflies often hatch during midday. Target fast water with a dry-dropper rig.
Green Drake (Ephemera guttulata)
- Timing: Late May–June (“the hatch of hatches”).
- Habitat: Fertile limestone streams.
- Key Rivers: Penns Creek, Fishing Creek.
- Patterns: Green Drake Dry Fly, Emergent Sparkle Pupa (size 8–10).
- Tips: The brief but explosive hatch draws trout to the surface. Don’t forget the Coffin Fly spinner fall at dusk.
Gray Fox (Maccaffertium spp.)
- Timing: Overlaps with Hendricksons and March Browns.
- Patterns: Adams Parachute (size 12–14), Quill Body Emerger.
Summer (July–August)
Sulphurs (Ephemerella invaria/dorothea)
- Timing: May–July (peaking in June).
- Habitat: Limestone creeks like the Letort.
- Patterns: Sulphur Sparkle Dun, CDC Transitional Dun (size 16–18).
- Tips: Match the pale evening dun (E. dorothea) in late afternoon. Watch for refusal rises—switch to a emerger or spinner.
Light Cahill (Stenonema ithaca)
- Timing: June–July.
- Habitat: Freestone rivers.
- Patterns: Light Cahill Dry, Partridge and Orange Soft Hackle.
- Tips: Fish dries in riffles; nymphs work well in deeper runs.
Trico (Tricorythodes spp.)
- Timing: July–September (morning spinner falls).
- Habitat: Spring creeks and slow pools.
- Patterns: Trico Spinner (size 22–24), Griffith’s Gnat.
- Tips: Use 6x–7x tippet and focus on smooth drifts.
Terrestrials
- Ants, Beetles, Grasshoppers, and Japanese Beetles dominate summer menus.
- Patterns: Chernobyl Ant (size 10–12), Dave’s Hopper.
- Tips: Target overhanging banks on windy days.
Fall (September–November)
Isonychia (Slate Drake)
- Timing: September–October.
- Habitat: Fast, oxygenated water.
- Patterns: Isonychia Nymph (size 10), Stimulator (orange or yellow).
- Tips: Nymphs are active swimmers—imitate with quick strips.
October Caddis (Dicosmoecus spp.)
- Timing: Late September–November.
- Habitat: Larger rivers and freestone streams.
- Patterns: October Caddis Dry (size 8–10), Peacock Caddis Larva.
- Tips: Fish dries near undercut banks at dusk.
Blue-Winged Olives (Fall Replay)
- Timing: October–November.
- Patterns: BWO Sparkle Dun, WD-40 Nymph (size 20–22).
Midges
- Timing: Year-round (peak in winter).
- Patterns: Zebra Midge (red or black), Griffith’s Gnat.
- Tips: Fish tiny dries or nymphs in tailwaters like the Delaware.
Regional Variations
- Limestone Streams (e.g., Letort, Big Spring): Rich in Sulphurs, Scuds, and Craneflies. Slow, clear water demands stealth and precise presentations.
- Freestone Rivers (e.g., Youghiogheny, Loyalsock): Home to Stoneflies (e.g., Golden Stones in June) and robust Caddis hatches.
- Tailwaters (e.g., Delaware River): Consistent flows support year-round hatches, including midges and BWOs.
Hatch-Matching Strategies
- Carry Stage-Specific Flies: For every hatch, have nymphs, emergers, duns, and spinners.
- Prioritize Presentation: Drag-free drifts for mayflies; skitter caddis dries.
- Monitor Water Temps: Hatches stall if temps drop suddenly.
- Fish the Shadows: Trout often feed in shaded areas during bright days.
Conservation Note
Pennsylvania’s trout face pressures from warming waters and habitat loss. Support organizations like Trout Unlimited and practice catch-and-release with barbless hooks to preserve these fisheries.
Get on the Water
From the Quill Gordon’s early whispers to the October Caddis’s autumn crescendo, Pennsylvania’s fly hatches offer endless opportunities for anglers.
By studying insect behavior, refining your fly selection, and respecting the ecosystem, you’ll unlock the secrets of the Keystone State’s waters.
Whether you’re stalking wild browns on Penns Creek or battling smallmouth on the Susquehanna, Pennsylvania’s hatches promise unforgettable days on the water.
Grab your fly box and waders—the next hatch is rising!
Pennsylvania Rivers by Region
Northwest
- Allegheny River
- Caldwell Creek
- Hickory Creek
- Little Sandy Creek
- Neshannock Creek
- Oil Creek
- Slippery Rock Creek
Southwest
- Clear Shade Creek
- Dunbar Creek
- Laurel Hill Creek
- Meadow Run
- Loyalhanna Creek
- Little Mahoning Creek
- Youghiogheny River
North-Central
- “Big” Fishing Creek
- Clarion River
- First Fork Sinnemahoning Creek
- Kettle Creek
- Lycoming Creek
- Penns Creek
- Pine Creek
- Slate Run
- Cedar Run
- Sinnemahoning Creek
- Spring Creek
- Young Womans Creek
South-Central
- Big Spring Creek
- Clark Creek
- Codorus Creek
- Falling Springs Branch Creek
- Letort Spring Run
- Little Juniata River
- Spruce Creek
- Yellow Breeches
- Yellow Creek
Northeast
- Lehigh River
- Pohopoco Creek
- Big Bushkill Creek
- Bowman Creek
- Brodhead Creek
- Fishing Creek
- Lackawanna River
- Lackawaxen River
- Loyalsock Creek
- McMichaels Creek
- Pocono Creek
- Tobyhanna Creek
Southeast
- Bushkill Creek
- French Creek
- Little Lehigh Creek
- Manatawny Creek
- Monocacy Creek
- Saucon Creek
- Tulpehocken Creek
- Valley Creek
- West Branch Octoraro Creek
- Wissahickon Creek
Steelhead Alley
- Cascade Creek
- Crooked Creek
- Elk Creek
- Sixteenmile Creek
- Twentymile Creek
- Walnut Creek