It is with great pleasure we can say the fall green drakes (#10 primarily) and flav’s (#12-14) have begun. You’ll find these 2 large mayflies hatching sometime between 2 pm and 5 pm most days for the next 4 weeks or longer. Emergers and Duns will serve you well. 
While these are important hatches and my personal favorites, let me explain the other hatches and where you might find them throughout the different sections of the river:

PMD or Pale Morning Dun #16 & #18. Should be found Upper Middle and Lower River and mostly later in the afternoons, although on hot days you could see the hatch delayed to evening hours. Make sure to add Cripples and Emergers to your box, and of course a great Dun is important and critical at times. These turn into Rusty Spinners after the last molt and females hit the water in the evening, usually at Dusk. 

BWO or Blue Wing Olive #18-22. With cooler weather bound to happen in the coming weeks these could change to a mid afternoon hatch and happen all segments of the river. Right now, most of the BWO’s we’ve been seeing are around the hatchery and happen as the shade hits the water in the late afternoon. Just like the PMD’s above, you’ll need all the stages to fool Metolius fish. I’ve been loving little CDC flies these last 2 seasons and the Shuttlecock type flies have become staples in my boxes. 

Pale Evening Dun or PED #14. This is not a super common occurrence I have witnessed on the Met, but Sunday afternoon I saw a bunch of them hatching. Not a bad idea to have a Yellow Soft Hackle and a Yellow Comparadun when these are hatching. 

Mahogany Dun #16 will become more prevalent as September moves on, but there are a few around already. Our Upright Rusty, Quill Gordon, Purple Haze and Grey Comparadun are all great flies to match this hatch. You’ll see them all over the river from Lake Creek down to Bridge 99 and below. 

Caddis hatches have been massive. It seems the clouds of little yellow caddis have slowed already, but there are a ton of bigger yellowish-tan caddis in a #16, plus tan #16, grey #12-16, olive #16-18 and the 1st october caddis #10 were seen over the weekend on our camp trip to the river. Caddis won’t slow down much until later in October, and some of these will go well into winter. Caddis love all stretches of the Metolius, in fact the type of water the Metolius is just kind of makes the whole river a caddis factory. 
I worked the fly shop today and realized the boys had sold the living daylights out of caddis lately and our election was low, so I did an emergency re-order of some of our favorites and they will be back in stock by the end of the week. Some of these caddis are also used to match the little olive stones I talk about next….

Stoneflies become more and more important in September, with little olive stones #16-18arguably the most important later in the day and early evening. Our Double Wing (CDC) Stone, Hemingway and other cool little CDC concoctions seem to work best when matching this hatch. 
(Ben M this is your answer) One of our customers wrote and asked about my last report, and wondered when I was talking about all those big stones if I meant the nymphs, or if I was talking adults. This time of year, we have AT LEAST 4 different stoneflies hatching. So adults are what I am mostly talking about. Cascade Stones (we formerly called them Willowflies) are just starting and could be found anywhere, but most likely from Candle Creek up to about the Gorge Campground. These are big, #4 and #6. Do the fish go nuts for them? Not usually, but would I have a #4 or 6 Dark Chubby in my box in September if I saw some crashing rises. Yep.
Same goes for Salmonflies in a #6-8. I’d have a Chubby or big Norm Woods in Rusty Orange at the ready just in case. Again mostly from Bridge 99 to Gorge. I’ve seen fish crush these at the Dolly Hole at dusk in September. 
One big stonefly that is more consistent in September (and likely October) is the Golden Stone. These #8-10 stones are very important and can pop up in isolated places like the gorge, the canyon, the Dolly Hole and way down below Bridge 99. But where you should see most of them this month is above Gorge up to Tract C. We like Clarks Stones and Norm Woods Specials to match this hatch. 

Midges may be important. Griffiths Gnats in a #20-22 might be good to carry this month. I hate to tell this story, but last year we were out fishing a favorite spot, with a really nice trout rising consistently to god knows what. I put about 15 flies over that fish, and had some looks but never a commitment. My friend Dean was with me and put a few casts and a few of his flies over that fish with the same results. The next day, Dean went back and put a Griffiths Gnat over that fish and caught it right away. So, there you go. 

Terrestrials Ants, Beetles and lots of Hoppers out this time of year. None of these are my 1st choices on the Metolius almost anytime, but all of them have been productive at times. 

There are no Kokanee running up the river yet, so eggs are not yet on the menu. 

There are a lot of Bull Trout in the river and fishing has been really good on Streamers mostly, but nymphs will take there fair share of Bulls, and a Balanced Leech or MOP under an indicator is pretty good at times.