Revealing the Bugs of the Underworld

This article originally appeared in the February 2009 issue of Fly Fisherman.

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For much of my life, I’ve been swimming in bug stew and watching how fish react to their food. When Lisa and I began our fly-fishing school more than 25 years ago, we started photographing aquatic insects and fish in an attempt to bring the trout’s world into the classroom. It was a good start, but we soon realized that if a picture is worth a thousand words, then a video is worth a million. We switched from taking stills to shooting video, and over a decade of shooting, compiled enough material to produce the aquatic insect documentary Bugs of the Underworld.

Bugs of the Underworld is not a fly-fishing DVD, but its relevance to fly fishers is obvious. Being underwater and seeing how a bug behaves in its natural environment is by far the best way to learn how to design an imitation and make it behave like the real thing.

Watching an insect in slow motion brings to light many nuances that escape casual observation. Seeing how a giant stonefly nymph tumbles in the flow runs counter to accepted fishing dogma; however, what are you going to believe, urban legend or your eyes?

The following is some of what we learned in the course of 11 years filming Bugs of the Underworld.

Damselflies

Though many anglers fish damselfly nymphs, the most vulnerable stage of a damselfly’s life is when an adult female is laying eggs underwater.

A female damselfly crawls underwater to deposit her eggs onto vegetation. She has rudimentary lungs rather than gills and must carry an oxygen supply with her. Her entire body is cloaked in a film of air that glistens like a mirror and can be seen from long distances underwater.

Once she is done laying eggs, she releases her grasp and allows the buoyant air sheath to float her passively to the surface. She can’t swim, run, fly, or hide, and her brilliant, shiny form is blatantly obvious to the trout. When trout key in on egg-laying damsels, little else grabs their attention.

Unlike adult damsel patterns found in fly shops, with their wings neatly splayed out to the sides like a pinned butterfly, naturals hold their wings tight above their backs to hold a capsule of air. Until someone comes along and sells a realistic pattern, you’ll have to tie your own, which isn’t difficult. All you need is a thin body of braided backing colored with Veniard’s Kingfisher Blue dye—and banded with a black felt pen—with a loop of white Zelon sticking out the back. Forget about eyeballs and other fancy trimmings. It is the general shape, the mirrorlike reflection, and the drifting behavior that make trout drool.

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Shake the damsel imitation in a bottle of fine fly desiccant (Loon Outdoors Dust or Frog’s Fanny). The powder repels water to create a shimmering glow around the fly. For fun, poke your finger in the bottle of desiccant and then stick it into a glass of water. The quicksilver sheath coating your finger is amazing. Dry-fly shakes and powders are made from silica (glass) dust and are harmless to you and the environment.

To fish the fly, add split-shot near the tippet knot and cast into your favorite stillwater. Like a little blue angel, the sparkling, buoyant damsel rises, then hovers in the water above the shot. You can jig the fly down and up by making slow retrieves punctuated with long pauses. When the fly no longer sparkles or floats, treat it with desiccant powder again.

Midges

Emerging midge pupae (and some mayfly nymphs) often anchor the tip of their posterior to the underside of the surface film, then arch their backs and attempt to lever, or pry through the rubbery meniscus. I have never seen this described in any of the literature, but it is so distinctive and common across all water types that I can’t help but feel that fly fishers are missing out on an extremely important opportunity. The photo in this article helps convey the idea, but seeing the actual process on video helps you to fully appreciate it.

This arching creates a distinctive U shape, and the surface film reflects an image of the insect’s back. It is the exact opposite of the impression given by typical “hunchback” nymph patterns on scud hooks. Often there are hundreds—sometimes thousands—of arching insects within sight. Most normal patterns look entirely out of place, and are invariably scorned.

I’m at a loss trying to make a suitable imitation, and my hope is that some creative fly tier will be inspired to concoct a realistic pattern. I’m certain this entirely new genre will become a must-have for fishing to selective midging trout.

One of fly fishing’s most pervasive myths is that midge pupae ascend through the water column at less than a snail’s pace. The midge pupae I’ve observed, especially chironomids (chronnies or chromies) race to the surface by using a wavelike undulating motion that turns the entire body into something like a dolphin’s fluke.

I’ve followed midges for 30 or 40 feet underwater, and they never slow down. At times they ascend so quickly that I can’t safely follow them upward using scuba gear.

When there is a slight breeze, a great technique for fishing chironomid pupa imitations in stillwaters is to use a floating line with a leader/tippet combination that gets the imitation to the right depth (sometimes 30 feet or more).

Using tandem- or three-fly rigs (where legal), let your flies settle to the correct depth—at or near the bottom—then mend the line so it develops a big bend. Breeze on the water drags the line and pulls the flies upward.

Watch where the leader penetrates the water, and set the hook on any pause or change of direction. Don’t wait to feel anything! It is an extremely smooth retrieve, and you never lose contact with the fly, so you detect more grabs than with standard stripping methods.

Snails

Snails are vastly underrated as trout prey. In waters where anglers see damselflies, scuds, leeches, and midges, trout actually consume more snails by volume than all the aforementioned species combined.

It only makes sense—snails are large, easily captured packets of food that can occur in boggling numbers. Aquatic snails are 17 to 20 percent protein, and a single snail the size of your thumbnail provides more calories than many dozens of midge pupae. Snail meat is low in fat and carbohydrates and has virtually no fiber. The shell is a tremendous source of calcium. Atkins would approve.

Of course, snails crawl over the cobbles and amid the weeds, but trout most commonly find snails when they drift, completely exposed, underneath the

surface film. Snails can fill their shells with gas and float to the surface, where they are dispersed by wind and waves, or they crawl upside down with their foot attached to the meniscus. Gas-filled snails glow incandescently as the sunlight penetrates their hollow, translucent shells. Snails hunting under the meniscus (they graze on diatoms and other food trapped against the sticky film) are enveloped in a telltale silver halo as their foot pulls down on the meniscus, creating a concave, light-trapping lens.

The riseform of a snailing trout is virtually nonexistent. One second the snail is there, and the next it is plucked off with a subtle popping sound.

Make a simple—yet effective—snail imitation by wrapping yellow/olive Krystal Chenille into a ball around the shank of a hook, then wind a few turns of stiff hackle at the eye. The hackle lies in the film and creates the silver halo, while the translucent chenille glows when it is backlit. Perfect.

Stoneflies

Despite countless articles to the contrary, we have never encountered Little Yellow Stoneflies (Isoperla) hatching up through the water column. From the bank, many of these hatches appear to be midwater emergences, and many other anglers share that opinion, but underwater we saw something different.

Instead of myriad Little Yellow Stonefly nymphs swimming for the surface to emerge, we saw adult stoneflies lying flush on the film, apparently exhausted from egg laying. We’ve seen adults get a second wind and launch back into the air, which from shore looks exactly like an emergence.

Some stillwater “winter” stoneflies (Capnia) do emerge through the film, so I won’t categorically say that Little Yellow Stones can’t—it’s just that in hundreds of subsurface encounters, Lisa and I have never seen it.

Try using a spinner pattern when you think stoneflies are hatching in open water. Mayfly spinners look similar to spent ovipositing stoneflies.

Stonefly nymphs are weak swimmers, and we frequently see the nymphs drifting helplessly in the current. In the water, they are virtually weightless and do not bounce along the bottom like common lead-loaded nymph patterns.

A drifting stonefly nymph is much better imitated by an unweighted pattern kept close to the bottom with split-shot. A tethered nymph wafts with the currents and acts convincingly alive.

Put the Brakes on Your Drift

The stream-bottom flow—where nymphs and dead terrestrials are often carried—is much slower than the surface flow. Nothing looks more out of place than an artificial nymph racing along the bottom, bypassing all the naturals that are traveling the same speed as the current.

If your indicator is drifting at the speed of the surface current, it means that your nymph is being pulled along quicker than any natural.

When short-line nymphing, I continually jig the fly up and down during the drift. Each jig is actually a sharp hook-set. By keeping the rod tip upstream of the fly, I ensure that the jigging motion pulls the

fly slightly upstream, periodically helping to slow the drift. An ascending nymph is not only a strong feeding trigger—it also gives you a much better opportunity to “accidentally” set the hook than with a normal drag-free drift.

Kick the Drag-Free Habit

We have all heard and practiced the “drag-free drift” mantra for so long that most people forget many mayfly nymphs and caddis pupae are extraordinarily strong swimmers. [See “Nymphing is a Drag” by Jim Cox, December 2008. The Editor.]

Passive drift, whether it is behavioral or catastrophic, only occurs at brief moments in a nymph’s life. Non-swimming nymphs survive by clinging tightly to the bottom. The nymphs and pupae seen most frequently by trout are swimming, or at least ascending toward the surface.

That said, don’t discard drag-free drift, but mix it up by fishing your nymph like a small streamer. When a mayfly nymph or caddis pupa rises through the water column it is pumping and jinking toward the surface. A dead-drift imitation won’t cut it.

Retrieve your fly across the current at various depths and speeds. Stop and start your retrieves and, at the end of the drift when the fly is directly downstream of you, put some slack into the system by raising the rod tip to pull the fly toward you. Then quickly drop the tip to the water to create slack line. The nymph falls toward the bottom, and when the line becomes taut again it swims back up toward the surface. Killer.

Though our work was directed at aquatic insects, during our time underwater we couldn’t help but be impressed by the number of dead terrestrial insects drifting along the streambed. Terrestrials, almost by definition, don’t float and most quickly sink. Try fishing your favorite grasshopper, ladybug, or ant pattern with a split-shot. You might be pleasantly surprised.

Under the Film

Both mayfly nymphs and midge pupae use precious energy breaking through the surface film to hatch. In cold, humid weather it can be impossible for the bugs to break through, and thousands die underneath the film. I’m not sure if this is because the cold weather affects the insect’s metabolism or if it merely increases the tenacity of the surface film. Regardless, the insects are in an impossible fix, and under these conditions, trout expect to see their meal under the film rather than in it or on it.

When the weather is cold, take an appropriate nymph or pupa pattern, slobber and chew on it to get it nice and soggy, then attach it to a long tippet treated liberally with fly floatant. The treated tippet floats on top of the water and suspends your soggy fly just beneath the film, exactly where the trout want it.

Visiting the Underworld

If this article accomplishes nothing else, I hope it serves as a catalyst prompting you to grab a wetsuit and mask, drop through the looking glass, and visit the bugs and fish firsthand. It’s a whole different world down there, and frequently not what you might expect.

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Ralph Cutter is the author of Fish Food: a Fly Fisher’s Guide to Bugs and Bait (Stackpole Books, 2005) and the Sierra Trout Guide (Frank Amato Publications, 1991).