How to Pick the Right Fly (Part 5): Stoneflies 101

10 mins read

This is the fifth post in our series on how to pick the right fly. To see all the posts in this series, click here

By Spencer Durrant

Stoneflies are the Corvette of the bug world. Fast, nimble, and unquestionably attractive, in a mechanical sort of way. You’ll stare whenever you see one, but spotting them isn’t completely uncommon.

Trout treat stoneflies in a similar fashion. Usually, trout at least look at a stonefly as it drifts by. Unlike Corvettes, though, stoneflies garner attention from almost all trout.

These big bugs are a high-protein food source that most any trout will go out of their way to eat. When stoneflies are hatching in good numbers, trout tend to behave without their trademark skittishness.

That’s part of what makes fishing stoneflies so much fun. You get to throw big bugs – which are easy to see on the water – and often enough, you’ll catch big fish. That’s also why you need a well-rounded knowledge of stoneflies, so you can join in on the fun of fishing with them.

By the end of this post, you’ll have read all the need-to-know information about these big ol’ bugs.

What is a stonefly?

A stonefly is one of the largest aquatic insects commonly found in trout rivers.

Like most other aquatic insects, there are a few thousand different stonefly species in existence. For this post, we’re only focused on recognizing stoneflies by sight and matching them with common fly patterns.

Identifying a stonefly is really easy. They have a unique shape and silhouette that few other bugs share. They also have a simple life cycle, making it easy to match stonefly nymphs to patterns in your fly box.

So, that’s where we’ll start – identifying stoneflies by their shape and silhouette, and learning their life cycle. 

Stonefly Life Cycle

The stonefly life cycle is deadly simple: they start life as an egg, hatch into a nymph, then emerge into an adult.

Stonefly nymphs look an awful lot like mayfly nymphs, but there are a few differences to note.

First, a stonefly nymph only has two tails, compared to the three or more of a mayfly.

Second, stonefly nymphs have long, thick antennas.

Stoneflies spend one to three years as a nymph, growing larger all the time. When they grow, they push through their old exoskeleton, leaving behind a “husk” that you’ve probably seen on rocks, branches, and streamside vegetation.

As an adult, stoneflies look a lot like their nymph selves. They have a long, thick segmented body, two tails, long antennas, and two pairs of wings that fold over its back when not in flight.

Stoneflies return to the river to lay their eggs, but unlike other aquatic insects, they’ll do this multiple times before dying.

While stoneflies can hatch from February through August in some rivers, the hatches tend to get the most intense from April through August.

Identifying Stonefly Hatches

Unlike caddis or mayflies, most emerging stoneflies don’t get stuck in the surface film. When a stonefly nymph is finally ready to become an adult, it migrates towards land and sheds its old exoskeleton, leaving behind that classic stonefly husk. That movement towards land is a behavior trout will key in on, and that’s the closest to mayfly-like emergence behavior that most stoneflies demonstrate.

Once on land, stoneflies shed their exoskeleton and start taking flight. At this point, they’ll really only return to the water if they fall off a log, tree, or branch near the river, or to lay their eggs.

This is important to review, since “matching the hatch” in the sense of using the right emergers, cripples, spinners, or duns, doesn’t really matter when fishing stoneflies. What matters is recognizing a stonefly when it hatches, then identifying a good patterns to imitate that bug.

Now, stonefly hatches are very much time-dependent. Certain stoneflies only hatch during a specific time of the year, and often those hatches vary from river to river. Spending time researching the stonefly hatches in your area will always pay off.

For example – salmonflies hatch on the Henry’s Fork from May 20 through June 10. They hatch on the South Fork – not too far from the Henry’s – June 20 through July 5.

Knowing what stoneflies are hatching, and when, is key to getting in on the great fishing these bugs provide.

So, with that in mind, let’s take a quick look at some of the major stoneflies that hatch, some of their characteristics, and patterns to match them.


When it hatches: March – April/May

The skwala is the first stonefly of the year to hatch, and can come off in late February given the right conditions. Usually, the hatch kicks off in earnest in March, and it’ll last until runoff hits in most areas.

Skwalas are smaller than other stoneflies, and are usually dark brown in color.

Skwalas don’t hatch on every trout river. They’re common in Montana, Oregon, and Washington.

Yellow Sally

When it hatches: May – June/July

Yellow Sallies are another small stonefly, and start hatching in May. They’ll last through June and July, depending on where you’re fishing.

Yellow Sallies are super easy to identify – they have thin, yellow bodies with bright red spots near their tails.


When it hatches: May – June/July

Salmonflies are probably the most famous of all the stoneflies that hatch. These giant, orange bugs draw anglers – and trout – from across the country to fish their emergence throughout Montana and Idaho, specifically.

These are among the biggest stoneflies you’ll fish, and they’re easy to identify thanks to their bright orange color.

Golden Stonefly

When it hatches: June – July

Golden stones are more commonly found than salmonflies. They’re not as large, but they can be just as fun to fish. I’ve had some truly excellent days fishing golden stones in late June, after runoff subsides on many of the streams here in the Rockies.

The Flies You Need

Matching a stonefly to one in your box really only requires that you know what stoneflies are commonly hatching in a given river, at a certain time of year. Early on in the year, I have some extra skwalas in my box. As I get into May, I have Yellow Sallies, salmonflies, and golden stones on hand. I usually put my stoneflies away in favor of hoppers come mid-July. I will, however, keep stonefly nymphs in my box year-round.

With that in mind, these are some of the flies you absolutely need to have to get in on the action that a good stonefly hatch offers.

Getting Out There

Getting into great stonefly fishing is really about timing. These hatches can be quick and fierce, but they offer some of the best fishing you’ll have all year. Spend some time researching when stoneflies hatch on your local rivers, and make plans to be on the water during that time. Even if the water is high or off-color from runoff, fish will eat stoneflies.

When you catch some fish on stoneflies, be sure to let us know!



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