American Grannom

Often referred to as the Black Caddis
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Common Name: American Grannom (also locally referred to as Black Caddis)

Technical Name: Referred to as Brachycentrus, this genus is comprised of six species.

Habitat: This insect is widely distributed and common to most streams from the smallest streams to the largest rivers (Stream as Order: 2 – 5*) where moderate to fast currents flow over boulders, cobble, gravel and submerged logs and tree limbs.

Behaviors & Fishing Hints: Larvae build cases of small chips of bark formed in an elongated tapered four-sided chimney shape or of sand grains in a circular cross-section. The case is anchored to solid objects facing into the current enabling the larvae legs to be extended into the current to strain food particles with bristles arranged along the inner length of the legs.  Trout feed by picking encased larvae from their anchorage and when encased larvae drift in search of new living places.

Larvae form the pupa stage within cases and subsequently are readily fished while swimming to the surface to emerge and transform into an adult after struggling through the surface film and briefly flutter and ride downstream. The abdominal color is a key characteristic that changes over time; pupal and emerging adult color is bright to medium green and within days changes to an olive to tan brown color.

Mating swarms flutter and zig-zag at a low level over the stream and females, carrying a green egg bag on the tip of the abdomen, lay eggs on underwater objects by diving through the surface or crawling down from a protruding rock or waders of fishers. Pupal emergence and egg laying frequently occurs at the same time making it possible to fish subsurface with fly patterns mimicking both life forms (noon – dark); adult patterns also fish well in the surface film too as many females become entrained in the surface. 

Swinging flies, in teams of 2 to 3, across and down submerged in the upper portion of the water column to end with a Leisenring lift is an effective. Drowned adults also bounce along the stream bottom and are reachable with a deep running fly.

B. occidentalis emerges late April – May; B. americanus emerges July-Aug

Fly Patterns:

  • Larvae: Peeking caddis (bright green abdomen)
  • Emerger: Antron Caddis, X-Caddis and Soft Hackle (bright to medium green abdomen)
  • Adult: American Grannon, Hemingway Caddis, LaFontaine’s Caddis, Egg Laying Soft Hackle (olive to tan brown abdomen with green egg mass on tip)

Sizes: #14 – #16

Locations: Wide spread for example: Mecan, Wedde, Pine, Little Wolf and Flume

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