big-lost

Big Lost River is a river in Idaho.

It ranks #12 among the 28 waters of Idaho in the registry, and is of regional prominence.

Fished for trout (inferred from the species listed).

Species: rainbow trout, brown trout and cutthroat trout.

USGS GNIS record: 400591.

Stretches: Big Lost River Main Stem, Big Lost River Tailwater, East Fork Big Lost and North Fork Big Lost.

Features: Mackay Reservoir.

Sourced from 6 independent fly sites.

Sources: cdn.orvis.com (retrieved 2026-10-20), flylordsmag.com (retrieved 2026-10-20), lostriveroutfitters.com (retrieved 2026-10-20), The Perfect Fly Store, The Perfect Fly Store (2), Silver Creek (retrieved 2026-10-20), Silver Creek (2) (retrieved 2026-10-20), woodriverweekly.com and woodriverweekly.com (2).

Hatches

Baetis / blue-winged olive (below Mackay)

Stage: dun. Well sourced.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug hatching
  9. Sep hatching
  10. Oct
  11. Nov
  12. Dec

Size 20 olives in the August 2010 Silver Creek Outfitters post and size 20-24 late-morning olives (about 10 am-noon) in the late-September 2019 forecast, usually with a few tricos. Flylords adds spring and fall olives on the lower river.

Sources: Silver Creek, flylordsmag.com, Silver Creek

Craneflies

Sourced.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug hatching
  9. Sep
  10. Oct
  11. Nov
  12. Dec

Large craneflies fished with quartering-down presentations in the 2010 post; Flylords mentions summer cranefly patterns on the lower river.

Sources: flylordsmag.com, Silver Creek

Trico (below Mackay)

Stage: spinner. Sourced.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug hatching
  9. Sep hatching
  10. Oct
  11. Nov
  12. Dec

Size 20-22, building through late August in the 2010 post and present in small numbers in the September 2019 forecast. Lost River Outfitters lists tricos among the tailwater hatches.

Sources: lostriveroutfitters.com, Silver Creek, Silver Creek

Great red quill (Hecuba, upper drainage)

Stage: dun. Single or templated source.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug
  9. Sep hatching
  10. Oct
  11. Nov
  12. Dec

Late-September 2019 forecast: hatching on the upper Lost drainage, called the last big bug of the year; size 14 parachutes.

Sources: Silver Creek

Pink Albert

Stage: dun. Single or templated source.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug hatching
  9. Sep
  10. Oct
  11. Nov
  12. Dec

Size 16-18 in the August 2010 post.

Sources: Silver Creek

Black flying ants and hoppers (upper forks)

Stage: terrestrial. Single or templated source.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug hatching
  9. Sep
  10. Oct
  11. Nov
  12. Dec

Flying ants (size 14-18) matter more as August ends on the upper forks, with hoppers in play.

Sources: Silver Creek

Pale morning dun

Stage: dun. Single or templated source.

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug hatching
  9. Sep
  10. Oct
  11. Nov
  12. Dec

Upper forks: PMD (size 16) alongside black flying ants, Elk Hair Caddis and hoppers in the August 2010 post. Lost River Outfitters lists PMDs for the lower river without months.

Sources: lostriveroutfitters.com, Silver Creek

Also named, timing not yet researched: Yellow sally and gray drake (upper river), Stoneflies and caddis (tailwater).

Access, closures and rules change; check with the state agency before you go.