Grannom

Other Common Names: Mothers Day caddis, black caddis
Scientific Name: genus Brachycentrus

Grannoms build square-shaped cases and live in riffly water or runs with moderate to fast currents. Larvae are sometimes knocked loose, so a cased caddis pattern dead-drifted near the bottom might pick up some fish.

Pupation occurs in the same water that the larvae lived in. During a hatch, dead-drift a pupa pattern near the bottom in riffly water or just below riffles. An unweighted pupa pattern can also be drifted near the surface, or you can present a Soft Hackle with wet-fly swing. Another good strategy is a dry fly with a pupa pattern as a dropper or trailer; the dry fly acts as an indicator and sometimes is taken by the trout.

After the hatch, errant and unlucky adults fall onto the water, and a dry fly is the right choice. Bankwater downwind or downstream from overhanging trees is a good place to cast your dry.

Female grannoms swim or crawl underwater to lay eggs. You can fish a dry at this time, or go subsurface with a Soft Hackle or Diving Caddis pattern.

Grannoms hatch in spring and fall. The fall adults are smaller and are usually black, hence their nickname, "black caddis."

 

How to Match a Grannom

Hatches are matched from Westfly's database of "standard" fly patterns.

Larva
Size 12-16 Cased Caddis. Green
Riffles, moderate-fast runs; just below these: indicator, tight line
Pupa
Size 12-16 Soft Hackle. Body: green; Shroud: tan
Riffles, moderate-fast runs; just below these: surface swing, shallow nymph
Pupa
Size 12-16 Deep Sparkle Pupa. Body: green; Shroud: tan
Riffles, moderate-fast runs; just below these: indicator, tight line
Pupa
Size 12-16 . Body: green, dark brown; Wing: brown, black
Bankwater near foilage: indicator, tight line, shallow nymph
Adult
Size 12-16 Elk Hair Caddis, Parachute Caddis, X Caddis. Natural gray
Adult
Size 12-16 Goddard Caddis. Body: brown; Wing: black
Riffles, current seams, backeddies below riffles: standard dry fly, skating
Egg-layer
Size 12-16 Diving Caddis, Soft Hackle. Body: brown; Wing: black
Riffles, current seams, backeddies below riffles: surface swing, shallow nymph, rising nymph

 

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Characteristics

LARVA COLOR: Cream or green body

PUPA SIZE: 6-12 mm

PUPA COLOR: Body--Green body. Shroud--Tan

ADULT SIZE: 6-12 mm

ADULT COLOR: Wings--brown or black. Body--Green or dark brown.

OTHER CHARACTERISTICS: Larva live in square case made from plant material. Body, wing, and shroud colors can vary, so it's always best to check a natural insect where you are fishing. Body and wing colors will darken when the insect is ready to lay eggs.

 

More About Grannoms