Header image
Enter a name
Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Amphizoa (Amphizoidae) Beetle Larva from Sears Creek in Washington
This is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Caddisfly Genus Brachycentrus (Grannoms)

This prolific genus includes the popular eastern early-season Apple Caddis and Grannom hatches. Their life cycles are ideal for the fly angler, and every stage is frequent trout prey.

Note that this species changes color dramatically after it emerges, and imitations of egg-laying adults should be a different color from imitations of emergers. Emergers have pale blonde, almost off-white wings and bright green bodies, while the egg-laying adults have light brownish gray wings and medium green bodies.

Where & when

In 189 records from GBIF, adults of this genus have mostly been collected during June (25%), May (19%), July (18%), April (15%), August (12%), and September (6%).

In 140 records from GBIF, this genus has been collected at elevations ranging from 3 to 19029 ft, with an average (median) of 5659 ft.

Genus Range

Hatching behavior

Time of day : Usually afternoon

Most Brachycentrus species have very brief, very intense emergences on which trout feed steadily. Brachycentrus americanus is an exception, as its emergence may be more spread out.

The pupae are vulnerable to trout during their lengthy surface emergence.

Egg-Laying behavior

Brachycentrus adult females land on and ride the water calmly to oviposit, so they are well-imitated with traditional tent-wing caddisfly patterns.

Larva & pupa biology

Diet: Algae, plankton

Shelter type: Tapered wood cases of rectangular cross-section

Like many caddisflies, these larvae rappel between the rocks with a white silk anchor line. In Caddisflies, LaFontaine recommends imitating it by coloring the last eighteen inches of the leader white.

Special thanks to Lloyd Gonzales, author of the excellent new book Fly-Fishing Pressured Water, for helping to sort out the Brachycentrus species and common names.

Specimens of the Caddisfly Genus Brachycentrus

1 Female Adult
3 Adults
1 Pupa
2 Larvae

2 Streamside Pictures of Brachycentrus Caddisflies:

3 Underwater Pictures of Brachycentrus Caddisflies:

Discussions of Brachycentrus

Brachycentrus americanus on the Lower Sacramento River California
Posted by Troutguide on Oct 29, 2016 in the species Brachycentrus americanus
Last reply on Oct 29, 2016 by Troutguide
I believe this is the species found in sometimes very large numbers on the Lower Sacramento River in the Redding area. Ten years ago it was present in such large numbers that fishing a fly on the bottom resulted in frequently hooking one of these caddis still in its case. Along with other aquatic insects their numbers have declined to a fraction of once seen. I don't believe the egg Sac dropped by the females to be olive , instread I have seen it to be a bright green. The females seem to oviposit close to the edge of flowing water and not midstream.
grannom caddis
56 replies
Posted by Goose on Sep 26, 2006
Last reply on Feb 1, 2016 by Martinlf
Hi All! I was reading through the site and I happened upon the Grannom (Apple) Caddis page, which made me wonder. Here in PA it is called The Mother's Day Caddis, I believe. Adults, which trout rarely feed on, are imitated with black or peacock herl bodies. The pupa, or emrgers I guess, we imitate with a wet fly. It has a peacock herl body and brown hackle for the legs, etc. in a size 14. Is this the same Grannon as the apple Grannom? Just curious!
I still get confused by these caddis and I'm trying to narrow down a list of caddis patterns and colors to cover the largest percentage of the hatches throughout the year.
What's happening here?
5 replies
Posted by Troutnut on Jun 5, 2007
Last reply on Jun 6, 2007 by Troutnut
Check out the two streamside pictures on my Brachycentrus page. I found these clusters of dead grannoms in a few different spots along a Catskill river on May 12th, while many members of (seemingly) the same species were in the air laying eggs and occasionally falling spent and being eaten by trout.

Have you ever seen these clusters? What's the explanation?

Start a Discussion of Brachycentrus


Caddisfly Genus Brachycentrus (Grannoms)

Genus Range
Common Name
Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy