Fly Fishing for Trout Home
User Password
or register.
Scientific name search:

> > Arctopsyche grandis

This topic is about the Caddisfly Species Arctopsyche grandis

Gary LaFontaine regarded this species as very important in the West, and wrote of it in Caddisflies:

A. grandis is one of those special insects that is worth making the focus of a fishing trip because it gets the best trout in a river interested in feeding.

It owes much of its importance to its large size. Read more...

The Discussion

FlymonsterSeptember 8th, 2011, 1:55 am
Eugene, Oregon

Posts: 4
Here in the Willamette Valley the McKenzie Caddis (as Arctopsyche grandis is known locally) usually begins its emergence sometime around mid-May and can continue into mid-June. The most emergence activity will be noted on warm days once the water temperature reaches @ 52f. Most hatches occur on warm sunny days from 4pm-7pm. Arlen Thomason goes into great detail about the life-cycle and behaviors of a. grandis in his book "Bug Water".

At least for me, the McKenzie Caddis, marks the beginning of summer and excellent fly fishing for trout on the McKenzie, Middle Fork Willamette, North Fork of the Middle Fork Willamette, and our other local rivers and streams.
Fish or not to fish, there is no question.
EntomanSeptember 8th, 2011, 4:23 am
Northern CA & ID

Posts: 2604
Thanks for the input and welcome to the forum Flymonster. What sizes, patterns do you like? How do you like to fish the hatch?
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
PaulRobertsApril 12th, 2012, 11:12 am

Posts: 1776
A. grandis is abundant in the small mountain streams I fish here in CO. But I've yet to find where they and trout actually meet. Local lore has it they are mostly nocturnal. I've tied a full compliment of life stage imitations bc they are so abundant. Some day I'll put it all together.
EntomanApril 12th, 2012, 5:32 pm
Northern CA & ID

Posts: 2604
Paul -

That's my experience as well. The only place I've found them important where trout live is Rock Creek (if I remember right) and a day I once had on the upper Big Hole in Montana looking for grayling. They were both active midday.

I've heard about these big boys being important in Oregon, but I've never run into them (and I've fished there quit a bit over the years). Most hatch charts for the Mckenzie do show a large green caddis in size 8, but don't mention if they are talking larvae or adults. I have my doubts that grandis is found that low in a watershed, but I've never fished the McKenzie and was really interested to hear more of Flymonster's input. Unfortunately, it appears he was just another hit-and-run poster. :(
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
PaulRobertsApril 12th, 2012, 6:09 pm

Posts: 1776
There was a great write-up on them not that long ago by a guy on the MacKenzie. Can't find it now. The photos showed very large water and he described details in fishing that activity.
FlymonsterMay 16th, 2013, 3:36 pm
Eugene, Oregon

Posts: 4
Sorry about the post and run, and yes it has been some time. We are now seeing some emergence of A.grandis on the lower McKenzie (below Leaburg Dam all the way down). In my experience, we see more in the lower river than we do the upper river (Blue River and above) The middle McKenzie (Blue River to Leaburg Lake) there are a few but nothing like the lower river.
Typically, I'll use 8's, 10's, and 12's (10's being the go to) CDC green foam body caddis, and same size elk hair caddis with bright green bodies for dry. Karnopp's riffle diver in 10's and 12's for an emergent pupa. Many times tied off the bend of a dry @ 18-24". Warmer darker, overcast days will see the most activity during daylight hours. Also, late evening, just before dark on clear days. Once the emergence begins, it seems the trout pretty much go after them (A.grandis) with reckless abandon. this is a link to Arlen Thomason's write up which also appears in his book "Bug Water".
Fish or not to fish, there is no question.
FlymonsterMay 20th, 2013, 3:38 pm
Eugene, Oregon

Posts: 4
Also to add to what I witnessed yesterday 5/19/13. There was a rather decent emergence of A.grandis, the most I had seen at one time over the last 5 years, taking place in the lower McKenzie from around 5pm until 7ish pm. I wasn't able to capture any of them for a photo shoot, however I did notice several still VERY green (freshly hatched) flitting about, and many others that were significantly darker(older) egg layers. It was a fairly nice afternoon in the valley and only once the shadows got long did the majority of the appearances happen. However, much of the afternoon was spent pitching a CDC foam body caddis with good success.
Fish or not to fish, there is no question.

Quick Reply

You have to be logged in to post on the forum. It's this easy:
Username:          Email:

Password:    Confirm Password:

I am at least 13 years old and agree to the rules.

Related Discussions

TitleRepliesLast Reply
Re: North-East Canada Mayfly identification
(1 more)

In the Identify This! Board by JpMcKenzie
1Jan 28, 2018
by Taxon
In Brachycentrus appalachia Caddisfly Adult by Martinlf
Re: Emergence period of green drakes
In the Mayfly Species Ephemera guttulata by Beardius
5Dec 5, 2008
by Beardius
Re: collected from Bitterroot yesterday Drake
In the Identify This! Board by Leskorcala
4Jun 17, 2020
by Leskorcala
Re: Fishing with My Nephew: Eighth Annual Trip
In Fishing Reports by Martinlf
1May 31, 2022
by Jmd123
Brachycentrus americanus on the Lower Sacramento River California
In the Caddisfly Species Brachycentrus americanus by Troutguide
Re: The unusual weather
In General Discussion by Softhackle
4Mar 12, 2012
by GldstrmSam
Re: Flavalinea or Drunella Grandis
In the Identify This! Board by Byhaugh
10Dec 18, 2013
by Brookyman
Re: Site updates from July 1, 2017
In Site Updates by Troutnut
2Jul 2, 2017
by Jmd123
Re: Drunella grandis species complex
In the Identify This! Board by Crepuscular
2Aug 2, 2019
by Crepuscular