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3. Arctopsyche grandis

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.

Thanks for the input and welcome to the forum Flymonster. What sizes, patterns do you like? How do you like to fish the hatch?

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.

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. :(

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.

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.

http://www.west-fly-fishing.com/forums/ubbthreads.php?ubb=showflat&Number=337785 this is a link to Arlen Thomason's write up which also appears in his book "Bug Water".

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.