Stoneflies, East & West

The stream was sick. Leaking acid mine drainage had made some of its rocks look like toxic, rotting pumpkins. I was fishing there that late winter day simply because it was close to home. And because, against great odds, wild browns and stocked rainbow trout were eking out an existence in this place. Just like Dr. Malcolm’s line in the movie Jurassic Park, “Life finds a way.” But an ecosystem’s food chain is circular; trout could not live here without something to eat. And as I stood there in a little pool below a riffle, small black-colored stoneflies began buzzing across the surface like tiny float planes attempting on-water take-offs.

The fish noticed. Surface sips and splashes revealed one of the food sources that made trout life possible there. I’ve read—many times—that stoneflies can exist only in the cleanest, most pure water. But that isn’t always true. There are hundreds of stonefly species in North America. They are a vital trout food source along with other aquatic insects like mayflies and caddisflies which are, sometimes, better understood by anglers.

Nearly all stoneflies (order Plecoptera) complete their life cycles in the same fashion. They hatch from eggs into nymphs, and, depending upon their species, spend one to three years wandering river bottom cobbles grazing on bacteria, fungi, and detritus like miniature vegan crocodiles. But some species also crave a little meat—they hunt the nymphs and larvae of other aquatic insects. At approximately the same time each year, and always in precise species order, stonefly nymphs climb from the water onto dry areas to shed their exoskeletons and transform into adults. The adults mate on land, and the females lay eggs by dipping them into, or dragging them onto, the surface of the water to complete the process. In spite of the great number of North American stonefly species living in our flowing trout waters (you won’t find them in stillwaters other than, perhaps, areas near river inlets), we can organize these aquatic insects into four primary types for fishing in the Eastern and Western United States.

Little Black and Brown Stoneflies

Stoneflies in the families Capniidae, Taeniopterygidae, Nemouridae, Leuctridae, and others, are called by many angling names: Snowflies, Little Black and Brown  stoneflies, Slender Stoneflies, Early Stoneflies, Willowflies, Needleflies, and others. Though these stoneflies aren’t all closely related, I’ve lumped them into this group because they generally have a couple things in common. They are small, seldom achieving sizes larger than a #14 hook; some species barely fill a size 18. They are dark in color, ranging from pure black to a reddish or chocolate brown. Little Black and Brown stoneflies, along with midges, are generally the first aquatic insects anglers find streamside as late winter drips into early spring, though some emerge well into spring, and a few can be found in the fall.

The first to arrive are usually easy to find; their dark-colored bodies silhouette as they crawl along the snow and ice adjacent to open water. Females in some species have truncated wings. Some males are wingless. This usually keeps members of the Capniidae family from wandering too far after they emerge, and may be an evolutionary tactic to help protect them from flying into a predator’s radar at a time of year when insect options are few.

I’ve found little Black and Brown stoneflies to be much more important for trout fishing in the East  than those in the West, partly because some members of this group are more pollution tolerant, and therefore able to populate more Eastern waterways. Little Black and Brown stoneflies often provide anglers with some of the season’s initial dry-fly fishing opportunities. Fly tiers have designed specific patterns to imitate the adults, and, years ago, I even developed a couple of my own. But a correctly sized black or brown Elk-hair Caddis usually works as well as anything else. Trout sometimes key onto the adults buzzing across the water’s surface, so you may need to skitter your dry fly a foot or so ahead of sporadically rising fish—then let it float drag-free—to get their attention.

In the Rocky Mountain Region, Little Black and Brown stoneflies are most important pre-runoff. Reduced water flows at this time of year allow the fish to focus on tiny meals. I don’t recall ever finding targetable rising trout eating the adults in the Yellowstone River, where I do much of my late winter fishing. But I do see enough of them around to imitate their nymphs. Just like using an Elk-hair Caddis to imitate the adults, you don’t need an ultra-realistic stonefly nymph pattern to catch fish. Pheasant Tails, either natural or dyed black, will work and so will small black or brown Copper Johns and Perdigons. I generally dead-drift the flies, though I have had some success by gently pulling them toward shore to imitate the nymphs as they travel to emerge. These same nymph patterns and tactics will also catch Eastern trout.

Pteronarcys Stoneflies

Pteronarcys (genus) stoneflies, usually called Giant Stones in the East and Salmonflies in the West, constitute the most mythologized stonefly hatches in the United States. It’s easy to understand why—they’re huge, easily filling a 2XL size 4 hook, though some may be smaller or larger than that. Generally, the largest are females, and males are one to two sizes smaller.

Salmonflies are by far the most sought-after Pteronarcys hatches. I’ve witnessed them emerging in such immense numbers that the streamside vegetation strains beneath the burden of the insects’ weight, and you can scoop double handfuls of empty nymphal shucks in every river back eddy.

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But some Western anglers may be surprised to learn that fly fishers in the East can also target their own, more diverse Pteronarcys hatches. My time stream sampling along New York’s upper Delaware River and Penns Creek in Pennsylvania revealed robust populations of Pteronarcys biloba, also known as Knobbed Stoneflies due to the dinosaur-like appendages protruding along their nymphs’ backs. But these same waterways also maintain fishable populations of Pteronarcys dorsata and a couple of other less common Pteronarcys species, which can be identified by the existence, or lack of, spines along their nymphs’ bodies and wingcases.

Though it’s possible, and pleasant, to have multiple Pteronarcys species in the rivers or streams you fish, it’s completely unimportant for fly fishing. The nymphs and adults look similar enough that trout won’t refuse your offerings if you omit their small physical differences. In the East, you seldom find enough Giant Stones emerging at one time to form an intense hatch where fish become selective, though my friend Mark Celebuski told me about such an event. Many years ago, he was walking along the upper Delaware’s main stem when he discovered trout eating Giant Stones with such aggression that he said it looked like someone was throwing bowling balls into the water from the railroad tracks.

Most Eastern Giant Stonefly fishing is blind-casting nymphs and drys. Fish large black or brown stonefly nymphs drag-free in riffles, or choose a buoyant dry fly like a Stimulator and cast it to calmer areas in riffles and runs and to water adjacent to streamside vegetation, where a trout might be waiting for an occasional stonefly to impact the surface.

Most Western Salmonfly hatches will be comprised of the Pteronarcys californica species, though there are a couple less common species you could encounter. You can imitate all Salmonfly hatches with the same flies. Unlike Eastern Giant Stones, Salmonflies often emerge during the day, in intense numbers, with targetable rising fish. I’ve watched trout sip them from the surface like they were eating size 16 Pale Morning Dun mayflies, and also explode on them like a great white shark eating a seal.

Chubby Chernobyls, Amy’s Ants, and other large foam dry flies work well while the hatch is occurring and for some time afterward. But for year-round angling, Salmonfly nymph imitations such as black, brown, or orange-and-black variegated Pat’s Rubber Legs consistently catch fish.

Because Salmonflies have a three-year lifecycle, their nymphs are present in varying sizes all year. Some anglers have one tied to their leader every month of the year, often in tandem with a smaller trailing nymph to mimic whatever else might be hatching at the time. A few of my Eastern friends have been using Rubber Legs and Chubbies more often too, and reporting success. The only drawback to fishing Salmonflies is that due to their often heavy emergences, trout can become satiated and ignore flies, natural and manmade. It’s usually best to pursue the hatch as soon as the fish have seen enough naturals to target them—later in the hatch the fish can become stuffed and lethargic.

Golden Stoneflies

Pteronarcys stoneflies get all the angler glory, but Golden Stoneflies can offer longer-lasting fishing opportunities. Many anglers call any large yellow, tan, or olive, often mottled with black or brown markings, stonefly a Golden Stone. But some of these insects are very different from one another biologically, though not always for fishing purposes. Most Golden Stones are in the family Perlidae. But some, like the famous western Skwala spp., are Perlodidae. Fly fishers refer to the various Golden Stone species, as they often do with aquatic insects, with much more descriptive names: brown willowflies, stone creepers, beautiful stoneflies, embossed stoneflies, and others. Some Golden Stone species begin hatching simultaneously with Pteronarcys stoneflies in rivers and streams where they cohabitate. Western Skwalas appear well before Salmonflies, often in April before spring runoff.

Eastern anglers are much more likely to encounter Goldens than they are Giant Stoneflies. The best Golden Stonefly fishing is generally from late spring through early summer. I often find them emerging alongside Eastern Green Drake mayflies (E. guttulata) when that hatch wains.

In mid to late summer, many Eastern trout waters get low and warm and trout in heavily pressured fisheries can become wary of large flies like Yellow Rubber-legged Stimulators. But there can be exceptions. And as long as the water remains cool enough for ethical catch-and-release angling, blind casting a dry fly through riffles and runs can produce trout, especially if you use them as the lead fly with a small nymph dropper.

Golden Stone nymphs are present in varying sizes, year-round, in most trout streams. I prefer to imitate them with yellow and black variegated Pats Rubber Legs, but many other nymph patterns also work well. I seldom use these big, usually heavy, nymphs during late summer low flows unless I’m fishing a large, deep river, because they often snag on the bottom.

Skwalas are perhaps the West’s best pre-runoff stonefly hatch. But they don’t appear everywhere. My home river, the Yellowstone, has only a small, generally unfishable population. But Skwala fishing on Montana’s Bitterroot and other Western rivers can be excellent.

Most Western freestone trout waters (and some tailwaters too), will also have species of more common Golden Stones. The same dry-fly and nymph patterns used to imitate them in Eastern waters work well in the West.

Perhaps the West’s least understood Golden Stonefly is the Midnight, Short-wing, or Nocturnal Stone. This summer-emerging Golden Stone seems ever-present in waterways where they appear, and their sparse hatches can last more than a month. Nocturnal Stones emerge when it’s dark, so you’ll seldom see the adults, including the strangely flightless males. But each morning, you’ll notice empty nymph shucks scattered among the streamside rocks, indicating their presence. The flightless males often run across the water at night, and on some rivers, you can skate and wake large dry flies after dark to bring big fish to the surface.

Early morning nymphing, or using tan or yellow hoppers to imitate the males, can also be productive.

The Sallies

Adult Sallies (whether yellow, green, or olive) look significantly less menacing than their Pteronarcys and Golden Stone cousins. Some of them are cartoonishly cute, resembling stonefly gummy bears with their brightly colored and somewhat translucent bodies and wings. Most Sallies, also called Sallflies and Stripetails, come from the Chloroperlidae family, but anglers generally call any small (usually sizes 12 to 16) brightly colored stonefly a Sally.

The Sallies are summer stoneflies in Northern climates, though they can hatch earlier in Southern trout streams, generally trickling from cold, tree-canopied waters throughout their range. You can also experience Sally hatches in large, warmer primary rivers. But I find they are generally less important there, though there are exceptions, particularly in the Western United States.

When I imagine an Eastern Sally emergence, I picture cold, clear, tree-lined water tumbling from the mountains; the type of stream where you’d expect to catch brook trout, small wild browns, or maybe Southern Appalachian rainbows.

Larger waterways tend to have diverse habitats that allow varying aquatic insects to thrive. I seldom see a lot of Sallies in these rivers, and maybe that’s why I generally don’t imitate them there. But in cold, somewhat sterile tributaries, Sallies are among the primary food sources for trout in the summer. You can blind cast (you seldom see fish eating naturals) small Stimulators to mimic the adults, but a brightly colored Elk-hair Caddis with a dyed yellow or white wing is usually all you need. You seldom have to nymph these tiny brooks to catch fish, but if you choose to do so, a dyed yellow or olive Pheasant Tail will work. The best eastern Yellow Sally nymph fishing I’ve experienced is for fall-run Great Lakes steelhead. I’m not exactly sure why they work so well—maybe it’s their bright, fish-attracting colors—but Yellow Sally nymphs were among my best producers when I guided there.

Yellow Sallies are important in small streams for Eastern anglers, but in the West, they can be very important in large rivers too. Perhaps it’s because some Western primary rivers are more cold and turbulent than many Eastern ones, creating better habitat for the Sallies, which builds their populations to more fishable numbers.

I’ve fished Western Yellow Sally hatches that were as intense as a PMD mayfly emergence, with thousands of naturals in the air, streamside vegetation, and floating on the water. Trout love them, and it’s possible to find steadily rising fish eating Sallies along the shoreline and in riffles. The same flies I mentioned for targeting Eastern Sallies will also work in the West. But it’s sometimes important to imitate the Sally female’s bright orange abdomen. The orange coloration is actually their eggs, glowing through their mostly translucent abdomen.

In my The Bug Book: A Fly Fisher’s Guide to Trout Stream Insects (Headwater Books, 2016), I use a football analogy to describe the importance of the three major types of aquatic insects. I compared mayflies to quarterbacks and caddis to running backs and receivers. That left stoneflies as the big uglies: offensive linemen. But whether you live in the Eastern or Western United States, stoneflies are vital insects for fly fishing. And just as no quarterback would want to play without his offensive line, no American trout fly fisher should enter the game without being prepared to match the four general types of stoneflies.

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Paul Weamer is the author of Fly-fishing Guide to the Upper Delaware River (Stackpole Books, 2011) and Dry Fly Strategies (Stackpole Books, 2021). He is the owner/operator of Weamer Fly Fishing LLC and lives in Livingston, Montana, with his wife Ruthann and his English mastiff Olive.