Midge
Chironomidae spp.
Midge
- Peak week
- Year-round
- Intensity
- Heavy
- Time of day
- Midday
- Water temp
- 32–60°F · peak 40°F
Top flies
Griffith's Gnat #20-24 · Zebra Midge #20-22 · WD-40 #20
Reliable winter fishing
Hatch calendar
Letort Spring Run hatch calendar.
- Spring creek
- Catch and release / fly fishing only / barbless
- brown trout
- wild
The spiritual home of American technical limestone fishing — the river of Marinaro, Fox, and Shenk. Tiny flies, clear water, picky wild browns. Terrestrials in summer are as important as any hatch.
Verify with the agency before fishing
Fishing regulations change every season. This page is a summary maintained by Bield — bag limits, exact dates, and species-specific rules must be verified with TCO Fly Shop before each trip.
What's hatching now
May on the water.
Blue Winged Olive
Baetis spp.
Mayfly- Peak week
- Mar 25 – Apr 25
- Intensity
- Heavy
- Time of day
- Afternoon
- Water temp
- 45–55°F · peak 50°F
Top flies
Parachute BWO #18-20 · CDC Comparadun #18-20 · Pheasant Tail Nymph #18
Spring emergence
Sulphur
Ephemerella dorothea / invaria
Mayfly- Peak week
- May 20 – Jun 25
- Intensity
- Heavy
- Time of day
- Evening
- Water temp
- 55–68°F · peak 62°F
Top flies
Sulphur Parachute #16-18 · Sulphur Comparadun #16-18 · Sulphur Sparkle Dun #16
Tan Caddis
Hydropsyche spp.
Caddis- Peak week
- Jun 1 – Aug 30
- Intensity
- Heavy
- Time of day
- Evening
- Water temp
- 58–72°F · peak 64°F
Top flies
Elk Hair Caddis #14-16 · X-Caddis #14 · LaFontaine Sparkle Pupa #14
Hendrickson
Ephemerella subvaria
Mayfly- Peak week
- Apr 15 – May 5
- Intensity
- Moderate
- Time of day
- Afternoon
- Water temp
- 50–58°F · peak 55°F
Top flies
Hendrickson Parachute #12-14 · Red Quill Spinner #12-14 · Pheasant Tail Nymph #14
Grannom Caddis
Brachycentrus spp.
Caddis- Peak week
- Apr 25 – May 10
- Intensity
- Moderate
- Time of day
- Afternoon
- Water temp
- 52–62°F · peak 56°F
Top flies
Elk Hair Caddis #14-16 · Henryville Special #14-16 · LaFontaine Sparkle Pupa #14
Light Cahill
Stenacron / Leucrocuta spp.
Mayfly- Peak week
- Jun 1 – Jun 30
- Intensity
- Moderate
- Time of day
- Evening
- Water temp
- 60–72°F · peak 65°F
Top flies
Light Cahill Parachute #14-16 · Cahill Comparadun #14 · Light Cahill Spinner #14
Full year calendar
Twelve months on Letort Spring Run.
Each row is a hatch species. Bar color = type, opacity = intensity, peak month outlined. The current month is highlighted on the timeline.
MayflyCaddisStoneflyMidgeTerrestrial· peak month outlined · intensity = bar opacity · current month highlighted
Hatch species on Letort Spring Run
The bug calendar in detail.
Midge
Chironomidae spp.
MidgeMiddayWater-temperature trigger
30°F32–60°Fpeak 40°F80°F- Duration
- 52 weeks
- Also called
- Chironomids · Snowflies
Top fly patterns
- Griffith's Gnat #20-24
- Zebra Midge #20-22
- WD-40 #20
- Disco Midge #22
Year-round food source — the only consistent option on tailwaters in winter. On cold sunny days look for noses sipping clusters in slow water.
Blue Winged Olive
Baetis spp.
MayflyAfternoonWater-temperature trigger
30°F45–55°Fpeak 50°F80°F- Duration
- 6 weeks
- Also called
- BWO · Olive
Top fly patterns
- Parachute BWO #18-20
- CDC Comparadun #18-20
- Pheasant Tail Nymph #18
- RS2 #20
Most reliable Eastern hatch. Two emergences — spring (March-April) and fall (September-October). Best on overcast, drizzly days.
Hendrickson
Ephemerella subvaria
MayflyAfternoonWater-temperature trigger
30°F50–58°Fpeak 55°F80°F- Duration
- 3 weeks
- Also called
- Red Quill · Dark Hendrickson
Top fly patterns
- Hendrickson Parachute #12-14
- Red Quill Spinner #12-14
- Pheasant Tail Nymph #14
- Hendrickson Comparadun #14
First substantial mayfly hatch on most Eastern rivers. Spinner falls in evening can be as productive as the dun emergence.
Grannom Caddis
Brachycentrus spp.
CaddisAfternoonWater-temperature trigger
30°F52–62°Fpeak 56°F80°F- Duration
- 3 weeks
- Also called
- Apple Caddis · Mother's Day Caddis (East)
Top fly patterns
- Elk Hair Caddis #14-16
- Henryville Special #14-16
- LaFontaine Sparkle Pupa #14
- Green-bodied Caddis Nymph #14
First major caddis emergence of the year. Look for clouds of small dark caddis above riffles in late afternoon.
Sulphur
Ephemerella dorothea / invaria
MayflyEveningWater-temperature trigger
30°F55–68°Fpeak 62°F80°F- Duration
- 6 weeks
- Also called
- Pale Watery · Little Yellow May
Top fly patterns
- Sulphur Parachute #16-18
- Sulphur Comparadun #16-18
- Sulphur Sparkle Dun #16
- Pheasant Tail Nymph #16
- Sulphur Spinner #18
The most important mayfly hatch on Eastern rivers. Reliable emergence + spinner fall every evening for 4-6 weeks. Match the spinners with rusty-bodied patterns.
Light Cahill
Stenacron / Leucrocuta spp.
MayflyEveningWater-temperature trigger
30°F60–72°Fpeak 65°F80°F- Duration
- 5 weeks
- Also called
- Cahill
Top fly patterns
- Light Cahill Parachute #14-16
- Cahill Comparadun #14
- Light Cahill Spinner #14
Pale yellow-cream mayfly. Less intense hatch than Sulphur but reliable across many Eastern rivers in late spring through early summer.
Tan Caddis
Hydropsyche spp.
CaddisEveningWater-temperature trigger
30°F58–72°Fpeak 64°F80°F- Duration
- 10 weeks
- Also called
- Spotted Sedge · Cinnamon Caddis
Top fly patterns
- Elk Hair Caddis #14-16
- X-Caddis #14
- LaFontaine Sparkle Pupa #14
- Tan Caddis Soft Hackle #14
Workhorse summer caddis. Heavy emergences and egg-laying flights at dusk through summer. Drop a soft hackle on the swing during the evening.
Terrestrials
(beetles, ants, hoppers)
TerrestrialAfternoonWater-temperature trigger
30°F60–78°Fpeak 70°F80°F- Duration
- 12 weeks
- Also called
- Hoppers · Ants
Top fly patterns
- Foam Hopper #10-12
- Foam Beetle #14-16
- Para-Ant #16-18
- Chernobyl Ant #10
Not a hatch but the most important summer trout food in many Eastern systems. Fish tight to grassy banks and overhanging trees. Hopper-dropper rigs are deadly July through September.
Trico
Tricorythodes spp.
MayflyMorningWater-temperature trigger
30°F60–75°Fpeak 68°F80°F- Duration
- 8 weeks
- Also called
- White-Winged Black · Curse
Top fly patterns
- Trico Spinner #20-24
- Trico Parachute #22
- CDC Trico #22
Tiny black-bodied mayfly. The spinner fall — not the dun emergence — is the main event. Look for clouds of spinners over flat water at sunrise.
River info
- River type
- Spring creek
- Primary species
- brown_trout · wild
- Management
- Catch and release / fly fishing only / barbless
- Counties
- Cumberland County
- Elevation
- 480 ft
- Access
- Limited public access; Carlisle Borough park sections and PFBC easements. Crowded — fish off-peak.
Live water temperature & hatch alerts.
Bield Fish reads USGS gauges, watches for the trigger window, and pings you when Letort Spring Run hits the temperature for your target hatch.
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