Big three bugs

Catch trout all across Canada by imitating their favourite food—mayflies, caddisflies and stoneflies

1Fulling Mill

Duns. Emergers. Sedges. Ephemeroptera. When it comes to the little aquatic insects that make up much of a trout’s diet, the terminology that fly anglers throw around can be pretty confusing. It’s doubly so if you’re new to fly (or trout) fishing and just trying to select the right fly to use. But to make a reasonable guess at what’s in the river, all you really need is a little knowledge about what the fish eat.

The three most common aquatic insects that trout—plus bass, carp, panfish and sometimes even walleye—love to munch are mayflies, caddisflies and stoneflies. Coming in a variety of sizes, colours and shapes, complete with complex life cycles, they’ve inspired literally thousands of effective imitations. My choices tend toward patterns that are more universal and generally imitative, with lifelike movement in the water. So with just a couple of fly boxes, I feel equipped to fish for trout almost anywhere in Canada. Here’s a thumbnail guide to the big three aquatic insects, along with choice imitations and strategies for making them appear lifelike.

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Mayflies

Also known in some regions as shadflies or fishflies, mayflies are the best known and most often imitated trout food. Mayflies spend 99 per cent of their lives underwater as nymphs (above left), which are very important trout forage. When the nymphs are ready to mature, they rise to the surface and struggle to emerge from their husks.

Once they’ve emerged, the fragile adults—also known as duns—drift on the surface waiting for their wings to dry before they can fly away. Duns (above right) are easy to recognize by their long, slender bodies, triangular upright wings resembling a boat’s sail and helicopter-like flight. Depending on the species and conditions, mayflies can hatch individually, in small groups or in massive swarms. 

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Choice flies

Nymphs: American Pheasant Tail (above), Gold Ribbed Hare’s Ear, Prince Nymph, all with or without bead heads

Wets: Leadwing Coachman, Partridge and Orange, Hare’s Ear Flymph

Dries: Parachute Adams, Klinkhammer Special, Sparkle Dun (below)

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Strategies

Trout eat mayfly nymphs as the insects drift helplessly with the current, so imitations should be dead-drifted below the surface. To get the fly down, it can be internally weighted or sport a bead head, or you can add weight to the leader. Nymph fishing can be challenging. You need to get your fly in the strike zone without constantly hanging it up, maintain a drag-free drift and detect the subtle takes. This is where using a strike indicator is a big help.

Mayflies are especially vulnerable to predation as they rise and emerge; an easy way to imitate this stage is to use the classic down-and-across wet-fly swing. This tactic is a little out of fashion, but it works as well today as when it was invented two centuries ago. Not surprisingly, adult mayflies are imitated with dry flies, most often dead-drifted up and across the current. 

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Caddisflies

In Canada, caddisflies are more common and widespread than mayflies, yet receive much less attention—despite being a key, season-long trout food. Caddis can also tolerate warmer and less-pure water that’s unfit for many other aquatic insects, making them crucial in rivers subject to farm or municipal runoff. That includes such blue-ribbon rivers as Alberta’s Bow and Ontario’s Grand.

Also sometimes called sedges, caddisflies begin life as tiny wormlike larvae (above top), rarely longer than a centimetre. The larvae then form cocoon-like structures, emerge as pupae and rise to the surface, drifting long distances as they struggle to emerge into adults. When the adults (above lower) finally do emerge at the surface, they quickly take flight. In both appearance and flight, caddis closely resemble moths. They’re easy to recognize by their tent-like wings, which fold down along their body when at rest.

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Choice flies

Larvae: Green Weenie, Simple Caddis Larva (above)

Pupae: Ian’s Crunchy Caddis, La Fontaine Sparkle Pupa, Leadwing Coachman, Partridge and Orange, Hare’s Ear Flymph

Dries: Elk Hair Caddis (below), X-Caddis

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Strategies

Much like mayfly nymphs, caddis larvae are best fished on the dead drift, usually with an indicator. But the helpless emerging pupae, which are chunkier than larvae, are often more attractive to trout. Like larva flies, pupa flies can be dead-drifted, either deep or near the surface. You can also use the time-tested wet-fly swing to imitate emerging caddis.

Unlike mayflies, when caddis finally break the surface as adults, they take flight quickly. But while attempting to lift off, they often hop across the surface a few times, prompting trout to chase them like a dog after a ball. So, dead-drift a caddis dry fly, but when it stops floating naturally and starts to drag, let it move across the surface in little skitters. This can produce explosive strikes.

A significant number of caddis also fail to properly emerge, and drift in the surface film towing their shell. These injured bugs really fire up the fish, and that’s the idea behind a “trailing shuck” caddis dry fly such as the X-Caddis. I rarely see anglers fishing caddis patterns in tandem, but a pupa fly below a dry fly can be a lethal combination.

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Stoneflies

Ranging from one to four centimetres in length, stoneflies offer trout a real mouthful, and a heavy hatch can drive the fish into a frenzy. Although they are found across Canada, stones only live in water that’s cold, clear, clean and usually fast with a rocky bottom. The nymphs (above left) are bulky, with substantial legs and antennae. They live on the river bottom, but frequently get swept out of cover and into the flow, which is when trout pounce on them.

Once mature, nymphs crawl onto land to emerge. For anglers, a stonefly hatch is actually when the adult insects return to the river to lay eggs and die. You can detect recent stonefly activity by discarded shucks near the water. To identify adult stoneflies (above right), look for the distinctive long, veined wings, which lie flat along the back.

1Choice flies

Nymphs: Montana Stone, Girdle Bug (above), Bitch Creek

Dries: Stimulator, Rogue Giant Foam Stonefly (below), Elk Hair Caddis, Muddler Minnow (treated to float)

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Strategies

Stonefly nymphs are typically weighted and dead-drifted deep, often ticking bottom. As with mayfly nymphs, the easiest way to do this is with a strike indicator, but expect to lose some flies. That’s why I favour simple patterns that are inexpensive and quick to tie. As the late fly-fishing guide and innovator Ian Colin James once told me, “Flies aren’t your little buddies.”

Adult stoneflies are clumsy flyers, and sometimes get dragged under while laying eggs. So, as well as dead-drifting surface patterns, you can also skitter them like a caddis, or even swing them down and across stream, letting them slip under the surface. Stonefly-imitating dry flies are also good searching patterns when there’s no insect activity, since they offer trout such a meaty morsel.

 

Associate editor Scott Gardner has been tying trout flies since 1985, and occasionally catches a fish, too.

 

4Günter Bechly Wikimedia Commons

Primordial mayflies

Mayflies are among the world’s oldest surviving insect species, found in fossils dating back 320 million years. Unlike today’s delicate specimens, however, ancient mayflies had wingspans of up to 45 centimetres.