River Intelligence · Entomology

Read the Water. Match the Hatch.

Every river has an entomological fingerprint — the bugs it grows, when they hatch, and how trout eat them. Learn the bugs, cross-reference live flows, and fill your box before you go.

Hatching NowPale Morning Dun Green Drake Trico Sulphur Small Western Red Quill Flav Gray Drake Callibaetis Spotted Sedge Golden Stone Yellow Sally Brown Drake Pink Lady Terrestrials Scuds & Sowbugs

Encyclopedia Hatch Calendar River Fingerprints Match the Hatch Bug School

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Mayfly

Hatching Now

Brown Drake

Ephemera simulans

A big burrowing mayfly that hatches in a handful of evenings and brings the largest fish in the river to the surface. Blink and you miss it — but the fish that eat Brown Drakes are the ones you remember.

Order

Mayfly

Family

Ephemeridae

Genus

Ephemera

Hook

#10-12

Season · Peak Jun evenings

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

Brown Drake

Emergence Triggers

Water Temp

55–65°F

Flow

Stable early-summer flows over silt

Light

The last hour of light and after dark

Water Type

Silt-bottomed flats, slow margins, spring-creek edges

Lifecycle

How Trout Eat It — Stage by Stage

Nymph

Evening, pre-emergence

Burrower nymphs leave their silt tunnels and swim to the surface with an unmistakable wiggle. Fish a big nymph on a slow lift.

Match It

Brown Drake Nymph#10-12

$3.25

Dun

Dusk

A short, violent window at last light. Fish eat with commitment — the hard part is seeing your fly.

Match It

Brown Drake Dun#10-12

$3.50

Spinner

After dark

The spinner fall runs past legal light on many waters. If fish are still working when you cannot see, this is why.

Match It

Brown Drake Spinner#10-12

$3.25

Cross-Reference

Where This Bug Matters

Big Hole River

≋ Waterlands · Hatch data blends USGS gauges, NOAA temps & regional emergence records

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