January 25, 2023
By Paul Weamer
I found three trout rising in the confines of a small pocket in the Delaware River’s Lower East Branch. Pink Cahills (Epeorus vitreus) were emerging, fluttering away on gentle air currents through the soft light of a falling sun. I tied a size 14 Compara-dun to my leader and made an accurate cast. The fly landed, drifted a foot, and was gently inhaled by a healthy trout.
I released the fish, dried my fly, and cast to the next one. Just like the first trout, a white mouth opened, my fly disappeared, and another big fish flopped into my net. When I think back to that day, I’m surprised that I can’t remember if those trout were browns or rainbows or exactly how big they were, but I remember everything about the third fish, simply because it ignored my fly. I cast again and again, and kept casting for the next 15 minutes. But while the fish kept rising, it never seemed to even glance at my fly.
The problem couldn’t have been my leader length, tippet size, or lack of a good drift. All three trout had been rising very close to each other, and if all of those things were good enough for the first two fish, they should have worked for the third.
I cut the fly from my leader and sat for a few minutes, watching the fish rise. It wasn’t eating every Cahill that floated over it. This fish was picky. Finally, a mayfly emerged through the film, hopped once on the surface, and disappeared in a swirl. I knew what to do.
I tied on a Catskill-style Cahill and caught the fish on my first cast. It was a plump, 13-inch brook trout, the smallest of the three, yet the most difficult to catch—an Alpha Trout. What made the Catskill fly the right choice? With all the dry-fly styles available at your local fly shop—Compara-duns, Catskills, thoraxes, CDC or snowshoe emergers, parachutes, and others—how do you know which style of dry fly works the best?
While most trout often live by the “close enough” principle as they gleefully suck almost any fly pattern from the surface, some exceptional fish—I call them Alpha Trout—key on one or two attributes of an emerging mayfly, and they lock onto that, making them challenging to fool. Vince Marinaro spent a great deal of time and energy studying and writing about this phenomenon and what he called a “game of nods” in his book In The Ring of the Rise. Basically, his game involved changing one subtle dry-fly attribute and studying a trout’s reaction to it, and then repeating the process. Marinaro was trying to improve his fly patterns, searching, like many anglers, for the perfect fly to catch the most difficult trout.
The perfect dry-fly style, the one that works in every instance, doesn’t exist. But most fish aren’t perfectly selective either, so much of the time, it really doesn’t matter. If you fish mountain trout streams where the fish are always hungry and will eat almost any fly, then exacting imitation is seldom important.
If you’re a “fish counter” then it may not matter for you either. While I enjoy spending a half hour working one difficult fish, some fly fishers prefer to quickly move up and down the river, looking for the most cooperative targets while ignoring difficult fish. They simply want to catch as many fish as possible. There is nothing wrong with that approach if it makes you happy. But if you’re the fly fisher who wants to catch that special trout no one else was able to catch, then understanding the relationship between mayfly families and dry-fly styles may help you get closer to that goal.
The Four Food Groups
There are 23 mayfly families in North America that contain 106 genera (for a look at all the mayfly families and their genera visit the Purdue University website Mayfly Central at www.entm.purdue.edu/mayfly/na-species-list.php). Fly fishers generally divide mayfly nymphs into four broad groups: clingers, crawlers, burrowers, and swimmers. These categories help us describe how and where the insects live, and they can also give you an idea of which styles of dry flies might work best for imitating them when these nymphs hatch.
Let’s take a closer look at four specific mayflies from four different families that represent each of the four groups: Cahills (Epeorus spp.), Tricos (Tricorythodes spp.), Brown Drakes (Ephemera simulans), and Little Blue-winged Olives (Baetis spp.). I picked these mayflies because they are important to trout anglers from Montana to Maine. The methods and fly patterns described for these four mayflies produce excellent results for most other members of the same families.
Clingers: Catskill-style and Epeorus Cahills
The Heptageniidae family of clinger mayflies includes several Cahill genera (Epeorus, Maccaffertium, Heptagenia, Stenonema, and Stenacron), Eastern and Western March Browns (Maccaffertium vicarium and Rhithrogena morrisoni), and several other mayflies. The Epeorus genus is perhaps the most geographically significant across the United States. Epeorus vitreus, the Pink Cahill, can be very important in the East, and the most important Western species is probably the Pink Albert (Epeorus albertae).
Clingers usually live in gravelly stretches of moderate to fast moving water, though some can inhabit more placid currents. Some emerge near the surface, but others, like several members of the Epeorus genus, emerge on the stream bottom and swim to the surface as duns. Because they are already free from their nymphal shucks when they reach the surface, they usually escape to the air very quickly. That’s why you seldom see Cahill fly patterns tied with trailing shucks.
This information helped me choose the Catskill-style Cahill that the brook trout ate at the beginning of this story. After I saw the brookie eat the moving Pink Cahill, I knew that a Catskill-style fly would be my best option for imitating movement, though a thorax probably would have worked just as well.
Catskill and thorax-style flies stand high on their hackles and tails, with their bodies above the water. This posture gives the illusion of movement and even aids actual movement. Subtle breezes make these flies twitch on the surface. They can also be purposely skittered to look like insects trying to fly.
It’s rare for clingers to appear on the surface with an attached trailing shuck like a burrowing mayfly, though fly patterns that incorporate trailing shucks are fine for some species like Eastern March Browns. But Catskill and thorax ties are still good bets even for this hatch because fish are often feeding on the duns in riffles where Catskill and thorax styles ride high, dry, and visible to anglers.
Crawlers: Compara-duns and Tricos
Crawler nymphs are some of the most important and widely distributed in North America. The Ephemerellidae, Leptohyphidae, and Leptophlebiidae families all include crawlers. Ephemerellidae contains many of our most important mayflies: Hendricksons, Sulphurs, and Cornuta Blue-winged Olives in the East; and in the West, Green Drakes and PMDs. The Leptophlebiidae family includes Black Quills (Leptophlebia sp.) and various Paraleptophlebia species, also known as Blue Quills, while the Leptohyphidae family’s most prominent member is the Trico.
Crawlers live in varied habitats, so it’s common to find them anywhere from the edges of riffles to slow pools. But most crawlers migrate before emerging, moving from areas of current to slower water where they hatch. Their transformation methods often leave them riding surface currents for an extended period, sending them sailing down into pools even after emerging from the edges of riffles.
Because crawler duns are often in pools where fish can easily scrutinize artificial flies, I prefer the Compara-dun’s slim profile for imitating most of them, including Tricos. You can also tie the flies with a trailing shuck (a Sparkle Dun) to imitate emergers.
Male Tricos hatch in the middle of the night, so their emergence doesn’t provide many fishing opportunities. But females hatch in the morning, the exact time depending upon air and water temperatures. The hatching females are sometimes overlooked by anglers waiting for the spinner fall.
A nice flat pool below a riffle is a great place to fish a standard or CDC Compara-dun to trout rising to emerging Trico females. The sparse materials used to tie Compara-duns—dubbing for the body, CDC or deer hair for the wing, and a tailing material—makes it easy to tie these diminutive flies.
Burrowers: Parachutes and Brown Drakes
Burrowing mayflies are some of the most anticipated of the season. They are almost always large insects that sometimes hatch in incredible numbers, elevating their emergences to event status for fly fishers.
Burrowers live in small tunnels in the streambed. They are highly sensitive to light, and most often emerge in the last hour of daylight, early in the morning, or at night—though cloudy days or shaded areas along streams can instigate daytime emergences.
Most burrowers are members of the Ephemeridae family, which includes Eastern Green Drakes (E. guttulata), Dark Green Drakes (L. recurvata), and Yellow Drakes (E. varia), as well as all Hexagenias. There are a couple burrowers in other families that can also be important to anglers, including White Flies (Ephoron sp.) in the Polymitarcyidae family and Golden Drakes (Anthopotamus sp.), a strange mayfly that straddles the line between a burrower and a crawler in family Potamanthidae.
Brown Drakes (E. simulans) are one of the most important members of the Ephemeridae family because they thrive all across the country. It’s uncommon for one mayfly species to inhabit such a vast region.
My preferred dry-fly style for Brown Drakes during daylight hours is a parachute with a trailing shuck. I make the demarcation between daylight and darkness patterns for members of this family for a couple reasons. Parachutes ride flush in the surface film, right where Drakes and Hexes emerge, and a dark brown Darlon or Antron trailing shuck is an excellent imitator of a big burrowing mayfly’s nymph case—which often fills with air and floats while the dun is trying to escape.
But Brown Drake and other Ephemeridae emergences often become so intense, and continue well after dark, that the flush-riding parachutes become a hindrance because they are difficult to see in low light.
After dark, I prefer oversize Wulff and Catskill-style flies for imitating the big burrowers because they are more visible, and they float longer because of their thick hackle.
Swimmers: Curved Emergers and Blue-winged Olives
As their name implies, swimming mayflies are very mobile, flitting about streambeds like little fish. Baetidae is perhaps the most prominent swimming family of mayflies and includes the Baetis and Acentrella genera, mayflies we call Little Blue-winged Olives. These adept swimmers provide some of our staple hatches nationwide.
BWOs are famous for appearing on rainy days, often in remarkable numbers, and creating quite a surface feeding frenzy. They often emerge just beneath the surface, often during cold, wet weather at the beginning and end of the season. Because of these traits, they have a proclivity for difficult emergences as they struggle to flee their nymphal shuck. This makes CDC and snowshoe emergers with trailing shucks—tied on curved, fine-wire hooks—deadly.
The way a curved hook curls a brown Darlon or Antron shuck beneath the surface, while keeping the wing and some of the body above the water, is just the ideal imitation of the natural.
Gray Drakes (Siphlonurus sp.) and Slate Drakes (Isonychia sp.) are also swimmers, although they aren’t in the Baetidae family. They are more agile swimmers than Baetis and readily glide through riffles, while Little Blue-winged Olives generally prefer to spend their lives with short swimming jaunts along weed beds.
I’ve often read that all Isonychia emerge on streamside rocks, not on the water, and that occasional duns on the water have either fallen there or been blown by the wind. It’s true, many Isonychias do emerge on streamside rocks. You can see their shucks congregated there every spring and fall, but they emerge in the water too. I’ve caught most of my Isonychia-eating trout with CDC emergers.
I believe Isonychias must emerge in the river often enough for trout to key on them. I’ve found too many duns floating on calm, windless days to believe the shoreline-only emergence myth.
Game of Nods
Some fish are more discerning than others when they feed. Perhaps these difficult trout have been caught before. Maybe their discriminating natures are genetic. But these trout are often the ones we anglers really want to catch—the Alpha Trout. They are the big ones, or at least the ones most likely to get big.
So what is the secret for fooling these selective surface-feeding fish? The bugs they are eating will tell us, if we’d just pay more attention.
Will understanding these basic mayfly families, and the dry-fly styles that best imitate them, greatly increase the numbers of fish you catch this season? Probably not. But it might help you catch more of the trout you really want to catch—the ones that you’ll remember next season and beyond.
Just like Protestants, dry-fly anglers come in several flavors. If catching a lot of rising trout is more important to you than catching a few select fish, then that’s how you should create your memories streamside. But give me a game of nods with an Alpha Trout. Those are the moments I cherish.
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.