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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.

Lateral view of a Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington
I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing this one.
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.

True Bugs

This common name refers to only one order. Click its scientific name to learn more.

Insect Order Hemiptera

These are often called True Bugs.
The large, diverse family of "true bugs" contains several insects of importance to anglers, both aquatic and terrestrial.

Perhaps the best known are the water boatmen of Corixidae, which are a primary trout food source at times in many high lakes, spring ponds, and slow-moving rivers. They are generally aquatic, although they may come out of the water to mate. I have seen good numbers of them flying over a northwoods river in late March, a sight that had me baffled until I captured one of the odd insects that kept flying past me and plunging into the water.

Other aquatic true bugs have received very little attention in
fly fishing literature, but they probably deserve more, because they are among the largest insects native to the trout's environment. The giant water bugs of Belostoma are especially favored, but trout also feed on the water scorpions of Nepidae. I plan soon to spend more time researching and imitating these insects to confirm my hunches and early observations.

The most famous terrestrial members of Hemiptera are the cicadas, which make for good fishing on those rare years when a large brood appears. Late every summer some fly fishers turn to tiny related terrestrials they call Jassids, which are the leaf hoppers and tree hoppers of the families Membracidae and Cicadellidae.
Dorsal view of a Ranatra (Nepidae) Water Scorpion Adult from unknown in Wisconsin
Here's a big water scorpion (no relation to actual scorpions). These guys are just about the most sinister-looking creatures you could find, and what's especially creepy is that they can come up out of the water and fly around, as I learned when one left my aquarium and buzzed my head while I was peeking into the microscope at a mayfly nymph.

True Bugs

Scientific Name
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