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Fly anglers live for the "hatches" when trout erupt in a feeding frenzy over the mass emergence aquatic insects from the river's surface. In these moments, trout can become so focused on one specific type of prey that they will pursue only a skillful imitation. Anglers who study aquatic insects to meet this challenge find that they're as captivating as the fish themselves. Every species has its own story, its own personality. We cross paths with these characters at the climax of a perennial drama of life and death, and--as with any great drama or sport--every play means so much more when we know the players inside and out. It's not just about catching fish. It's about knowing the stream and loving everything in it.

Troutnut.com's aquatic insect encyclopedia is a guide to these players and their stories. Read about the behavior of each species and view thousands of closeup photos, or join the fly fishing forum to meet other devotees of the world's healthiest addiction. You can learn the basics of mayflies, caddisflies, or stoneflies. Or dive into the details of storied species like the Hendrickson hatch and the Hex hatch.

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The blog posts below describe every update ever added to Troutnut.com by myself (Troutnut) and other contributors, along with occasional other thoughts and stories from my adventures in fishing, hunting, research, and travel in Alaska and beyond.

Dinking around on a small stream

By Troutnut on September 29th, 2020
On September 29th I went up to the mountains to sight in my hunting rifle in advance of deer season. However, the custom ammunition I ordered was the wrong length and wouldn't fit into the chamber, so that job ended quickly. (I won't name the company, because they bent over backward to make it right, and I got it fixed by hunting season.) As a consolation prize to make the trip productive, I drove to a nearby stream and played with the colorful little rainbows and cutthroat trout on perdigon nymphs. As a bonus, I caught a striking and unusual species of Siphlonurus mayfly.

Photos by Troutnut from Mystery Creek #249 in Washington

Closeup insects by Troutnut from Mystery Creek #249 in Washington

Female Siphlonurus autumnalis (Gray Drake) Mayfly SpinnerFemale Siphlonurus autumnalis (Gray Drake) Mayfly Spinner View 8 PicturesI found this specimen and saw a few more of its kind during midday on a small, steep, rocky creek fairly high in the Cascades, different from the previously reported habitats of its species.
Collected September 29, 2020 from Mystery Creek #249 in Washington
Added to Troutnut.com by Troutnut on November 10, 2020

Boulder-hopping on the Middle Fork of the Snoqualmie

By Troutnut on September 22nd, 2020
I wanted to get out one fishing and hone my fledgling Euro nymphing skills one more time before today's major beginning to the fall rainy season, so last night I drove way up the Middle Fork of the Snoqualmie to fish a section of fast pocket water for a couple hours.

Working my way up the line of slippery car-sized boulders and fallen trees that comprise the river bank, sandwiched between the roaring whitewater and impenetrable vegetation, was as much an exercise in gymnastics as in fishing. However, I found plenty of what I came for: interesting nymphing water and very pretty, very small coastal cutthroat and rainbow trout. The largest of the couple dozen fish landed were a pair of 9-inch cutthroat. I could have found slightly bigger fish downstream closer to town, but the seclusion of the headwaters was worth the extra drive.

Photos by Troutnut from the Middle Fork Snoqualmie River in Washington

Quick evening on the upper Yakima

By Troutnut on September 17th, 2020
With smoke from the west coast wildfires beginning to clear just a little, I took a few hours to fish one of the nearest access points on the Yakima River, where the fish are small and the water uncrowded. There were some stoneflies and caddisflies in the air--I collected one of each, representing the most abundant species--but there weren't enough bugs on the water to get the fish rising, except for the abundant 3-inch-long Chinook Salmon parr. I continued playing around with my new Euro nymphing rig and landed several rainbows up to 12", including my first double on that rod.

Photos by Troutnut from the Yakima River in Washington

Closeup insects by Troutnut from the Yakima River in Washington

Male Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly AdultMale Onocosmoecus unicolor (Great Late-Summer Sedge) Caddisfly Adult View 15 PicturesI first just assumed this was Dicosmoecus based on anglers' conventional wisdom since it's a large orange "October caddis," but Creno set me straight. I should have keyed it out. After another look under the microscope, it lacks an anepisternal wart on the mesopleuron (Mesopleuron: The side of the insect mesothorax, and the part to which the fore wings are attached in mayflies.), which rules out Dicosmoecus. The midtibiae have 2 apical (Apical: Close to the apex; tip or end.) spurs and 1 pre-apical (Apical: Close to the apex; tip or end.) spur, and from there the color pattern of the wing points to Onocosmoecus. The location then narrows the species to unicolor.
Collected September 17, 2020 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020
Female Isoperla fusca (Yellow Sally) Stonefly AdultFemale Isoperla fusca (Yellow Sally) Stonefly Adult View 13 PicturesThe family ID on this one was a little bit tricky. Just going by the size, shape, and color, it looks like Chloroperlidae. However, the second anal vein of the forewing is does not appear to be forked, and the apical (Apical: Close to the apex; tip or end.) maxillary palpal segment is close to the length of the penultimate segment, both of which rule out that family. The position of the cubitoanal crossvein (Crossvein: Short cross-wise veins in an insect wing which connect the long longitudinal (length-wise) veins.) relative to the anal cell in the forewing -- touching it in this case -- indicates Perlidae (and it really doesn't have the "look" of Perlidae at all), but other characteristics, such as the metathorastic sternacostal sutures and lack of gill remnants, point to Perlodidae. That's the right answer. Moving on to Perlodidae, the key characteristics in Merritt & Cummins lead straightforwarly to Isoperla, and the species key in Jewett 1959 (The Stoneflies of the Pacific Northwest) leads to Isoperla fusca.

There is one caveat: That source does suggest a May-July emergence, whereas this one was collected in mid-September.
Collected September 17, 2020 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020

Smoky float down the Yakima Canyon

By Troutnut on September 12th, 2020
With limited weekends remaining for fishing before October gets really busy, my wife and I braved the smoke to float the Yakima Canyon from mile 20 down to Red's. We found very few steadily rising fish, just small ones sipping Baetid duns in a couple of spots, and picked up some rainbows up to 14" on miscellaneous attractor (Attractor: Flies not designed to imitate any particular insect, but to incorporate characteristics attractive to trout. When trout aren't feeding selectively, attractors often outperform careful imitations as searching patterns because they are easier to see and incorporate more strike-triggering characteristics. They include legends like the Adams, Bivisible, and Royal Wulff.) dries and nymphs. I've never seen so many deer along the canyon, perhaps a consequence of the fire burning out much of the adjacent habitat and feed a few weeks ago.

I did a fairly poor job of budgeting our time, stopping at every likely-looking seam early in the float and then having to blow through some of the best water in a rush to reach the landing before it was too dark to see. That's what I get for not learning the river yet. There were some nicer fish feeding at dusk and I missed a couple strikes, but I didn't have time to stick around and keep working on them.

Photos by Troutnut from the Yakima River in Washington

Closeup insects by Troutnut from the Yakima River in Washington

Exploring up the Skykomish

By Troutnut on September 10th, 2020
I've been meaning to check out the scenic country headwaters of the Skykomish for a while, more for the scenery and variety than for the fish, which I expected to be mostly the same 6-12" rainbows and coastal cutthroats found in all the other rivers on the west slope of the Washington cascades. I was also looking to practice Euro nymphing some more, and the Foss River has some ideal stretches of pocket water for that. Starting late in the morning, I was successful early and often. Then, toward mid afternoon, the action shut down completely. I went from catching fish in every pocket to seeing no sign of them in extremely inviting pools. The water temperature was optimal, but the fish were just off.

For the last hour of daylight I drove to the South Fork Skykomish and fished a couple of promising pools. Fish finally started rising intensely right at dusk (to what, I'm not sure), and I caught six small rainbows on dries.

Throughout the day there were no noteworthy hatches, but I did find a couple of bugs worth photographing. I'm especially curious what a near-mature Ephemerellid nymph was doing in the river in mid-September, but I've not yet had time to put most of my recently collected specimens under the microscope and see what they are.

Photos by Troutnut from the Foss River and the South Fork Skykomish River in Washington

Closeup insects by Troutnut from the Foss River in Washington

Male Doroneuria baumanni (Golden Stone) Stonefly AdultMale Doroneuria baumanni (Golden Stone) Stonefly Adult View 18 PicturesI found this stonefly on some streamside vegetation. I didn't see any in the air in several hours of fishing.
Collected September 10, 2020 from the Foss River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020
Ephemerella aurivillii Mayfly NymphEphemerella aurivillii  Mayfly Nymph View 11 PicturesThis is a puzzling one to identify and I'm not sure about the species. The maxillary palp (
The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.
The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.
Palp: A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the < />palpus.
)
is present and segmented, and the maxillary canines are not strongly serrate laterally. I think it's Ephemerella, not Serratella. The ventral (Ventral: Toward or on the bottom.) lamellae of the gills on abdominal segment 6 have a clear median notch with a depth at least half the length of the lamellae, which points toward a couple of uncommon species (most likely Ephemerella alleni), but the abdominal tubercles (
A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled.  They are especially large in this species.
A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled. They are especially large in this species.
Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.
)
and coloration don't fit that species. To add to the confusion, none of the above species are expected to emerge in the fall, as far as I know. I'm going to call this one Ephemerella aurivillii for now, but that's highly uncertain.
Collected September 10, 2020 from the Foss River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020
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