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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Larva from the Yakima River in Washington
With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.
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.

Giant water bug. This dangerous aquatic predator belongs to the species Belostoma flumineum, in a family known as the "toebiters"

Artistic view of a Belostoma flumineum (Belostomatidae) (Electric Light Bug) Giant Water Bug Adult from the West Branch of Owego Creek in New York
I'm glad I finally got one of these Belostoma water bugs under my good camera. I had been hoping to get one in my kick-net samples for a while with no luck, but I ended up finding this one drifting midstream just below the surface while I fished. I have frequently seen water scorpions do that, too, and I'm beginning to suspect that is a common situation travel for these large Hemiptera bugs, and perhaps the way trout are used to seeing them.
Troutnut
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Troutnut on Apr 24, 2007April 24th, 2007, 7:17 pm EDT
This is a new favorite specimen of mine.

I'll have a video up featuring this one showing its swimming posture, too.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Jmd123
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Oscoda, MI

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Jmd123 on Dec 7, 2009December 7th, 2009, 7:07 am EST
Watch out for that proboscis - I have heard that these guys can pack quite a wallop when they bite! It makes me wonder if a trout could choke one of these down without getting poked in the throat and then coughing it back up again...I have seen large Dytiscid water beetles in trout stomachs before, but they don't have a hypodermic needle for a mouth!

I would be curious to see if anyone has ever found one of these inside of a trout (or other fish, for that matter).

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Troutnut
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Troutnut on Dec 7, 2009December 7th, 2009, 1:42 pm EST
Back when I was just getting into fly fishing and still kept quite a few fish, I caught a couple ~17" browns with stomachs FULL of Belostoma flumineum. It even led me to a few unsuccessful attempts to tie an imitation that looked right and rode well in the water.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Jmd123
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Jmd123 on Dec 8, 2009December 8th, 2009, 5:45 am EST
Out of curiosity, where was this? And what sort of imitation did you come up with? Something beetle-like?

Back in my early trout-killing days, I caught a number of fish with large dragonfly nymphs in their stomachs. I made what I thought were pretty convincing imitations, but the trout never did respond. I was either not getting my imitations right or I was overestimating the importance of those big nymphs in their diet...?

Jonathon

P.S. Ever run into Lethocerus, the REALLY BIG water bugs?
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Bigfly
Truckee, CA.

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Bigfly on Dec 9, 2009December 9th, 2009, 2:59 am EST
I fish at Pyramid Lake Near Reno NV. They have a small(popcorn)beetle pattern they fish. I encountered a dragon fly migration there, so I morphed the pattern to match. Latter, I encountered the giant american water beetle. Morphed the pattern again. It fishes well as a floater, and can be fished on a sinking line as well,(I use a Rio 300 gr).
Has caught fish in both still and moving water. #4 steamer hook, Rainy foam core, longer shuck greenish gold estaz, green-brown barred rubber leggs, tan loco foam pulled forward over the back. Take a magic marker and doodle a bit on the edges and a line down the back. Finish with hard head to prevent tearing when Walter eats it! I think of it as a Tri-tip style offering! Bon appetit!
www.Bigflyguideservice.com
Jmd123
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Jmd123 on Dec 9, 2009December 9th, 2009, 6:08 am EST
That sounds like a good pattern, Bigfly. I myself have never really encountered much of a bettle "fall", but in my early days on the Maple River (Emmet Co., MI) I did notice a lot of little bright green weevils that seemed to end up inside of trout, especially brookies. My attempts to imitate them didn't produce much, either...

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Troutnut
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Troutnut on Dec 10, 2009December 10th, 2009, 3:05 pm EST
Out of curiosity, where was this? And what sort of imitation did you come up with? Something beetle-like?


The Bois Brule River in Wisconsin. The imitation was more like a sinking nymph in water-bug shape, with a synthetic body/wing... it didn't really work out. Maybe a foam fly heavily weighted on the bottom would be the key to stabilizing that pattern.

P.S. Ever run into Lethocerus, the REALLY BIG water bugs?


I've caught one or two, but never when I had my equipment around to photograph them for the site.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Jmd123
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Jmd123 on Dec 10, 2009December 10th, 2009, 5:08 pm EST
Jason, as an entomologist (MS, Michigan State, '91), I do have to say that I enjoy your photos. I have had a few opportinuties to do aquatic entomology in my consulting work, but not enough. Really, I wish I would get a bug job in the fall and get to spend our cold, nasty MI winters inside doing the ID...but of course, I have either ended up LAID OFF or doing wetland delineations in snow & ice...

Perhaps my best entomological job was out in Oregon, when I was a field scientist at a place called South Slough Reserve near Coos Bay. By my own count from adding up my data sheets I identified around 85,000 benthic inverts I collected from little coastal Oregon creeks. Crazy - like 3-4 familes EACH of stoneflies, mayflies, caddisflies, beetles, true flies, and a few odd worms or other inverts in a stream about 1 foot wide and 2-4" deep. Not to mention juvenile sea-run cutthroats and coho, sculpins, sticklebacks, giant salamander larvae up to 14" long (!!), etc. A very lush and green place...Nice to reminisce sitting in a cold basement in Michigan.

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Jmd123
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Oscoda, MI

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Jmd123 on Dec 10, 2009December 10th, 2009, 5:09 pm EST
P.S. Caught a juvenile (no wings yet) Lethocerus in OR while electroshocking for fish once...about 3" long.

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...

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