Build a Better Stonefly Nymph
Learn the basics of stonefly entomology, 
and tie a fly that 
matches the real 
insects living in 
your local stream.
Article and photography by 
Igor and Nadica Stancev

We see stoneflies throughout the spring and summer. Stoneflies are especially noticeable when the larger females try to fly and lift their meaty bodies high into the air. After years of growing in the rushing streams and rivers, the nymphs emerge to reproduce. When these insects appear, they attract the attention of the 
fish and birds, and also fly fishermen. Stoneflies are a feast that can’t be overlooked.

There are about 3,000 known species of stoneflies throughout the world, and more than 500 species in North America. The scientific name Plecoptera comes from the Greek words plectos, which means “twisted” or “folded,” and pteron, which means “wing.” In other words, a stonefly is an insect with a folded wing.

The order Plecoptera contains seven families. The families Leuctridae, Capnidae, Nemouridae, and Taeniopterigidae are approximately 4 to 12 millimeters long, and the hefty Perlidae, Perlodidae, and Chloroperlidae measure up to 40 millimeters long. Stoneflies generally live in clean, well-oxygenated water, and cannot tolerate chemical pollution. The presence of stoneflies is considered an indicator of clean, healthy, cold water; the absence of stoneflies indicates potential pollution problems. Most stoneflies live in fast-flowing streams and rivers containing stone and rocky beds; only a small number of species live in slow chalk streams or in lakes where wave action generates enough oxygen along the shoreline. The only stoneflies we know of that live in lakes are found in very cold environments such as Scandinavia and the Alps.
Stoneflies appear during springtime when the number of other aquatic insects is not so high, and some species continue hatching throughout the summer.

Only a few species of smaller stoneflies appear in the autumn. When large numbers of stoneflies hatch, almost all the trout 
turn their attention to this important source of food. This is a great time to be on the water.

A stonefly nymph’s abdomen contains 10 clearly distinct segments; the thorax has three sections, each containing a set of legs. A stonefly’s legs are strong and have clawlike points that firmly grasp the streambed. A pair of wing cases is rooted in two of the thoracic sections, and gill filaments, shaped like tiny bristles, are positioned on the sides of the thorax; the position of the gills is used to help identify the exact species. Nymphs have two segmented tails that are usually shorter than the abdomen; keep this fact in mind when tying an imitation that matches the proportions of the real insect.


ImageThis is a fully grown Dinocras cephalotes nymph, which is dark brown and can grow almost 35 millimeters long, excluding the tails and antennae. The sides of the thorax have gray, bristlelike gills.

 
Live Long and Prosper
Smaller stonefly nymphs, such as the 15-millimeter-long Isoperla gramatica, have a one-year life cycle; bigger stoneflies, such as Dinocras cephalotes and Perla bipunctata, measure up to 35 millimeters long and require three years as nymphs to reach full size. The smaller species of stoneflies feed on algae, but larger stoneflies in the later stages of development are carnivorous and prey on the larvae of other aquatic insects.

Stonefly nymphs do not hatch on the water; this makes them very different from mayflies and caddisflies. Both mayflies and caddisflies have a stage of development entomologists call the subimago; most fly fishers refer to mayflies and caddisflies at this stage of development as emergers. The subimago is the stage of development between a larva and adult. A stonefly, on the other hand, does not evolve through the subimago stage; it transforms from a nymph directly into an adult.

When they’re ready to emerge into adults, mature stonefly nymphs crawl out of the water at dusk or dawn to avoid predators; because of their large size, many stoneflies are easy prey for fish and birds. The marauding insects find shelter along the riverbank under leaves, on rocks, and on the sides of trees and even buildings.

The body of an adult stonefly looks similar to the nymph, except it now sports wings. An adult has four wings of equal length that lie flat along the top of the insect. The wings feature prominent veins that are another key entomologists and hardcore fly fishers use for species identification.
Stoneflies are weak fliers; the males have slightly shorter wings than the females, which make them even poorer fliers. Males mainly leap, skip, and crawl, so successful mating depends more on the females locating males using knocking and pulsating sounds.

 Image
The body of an adult stonefly looks much like the nymph except that it has wings. If you see large numbers of adult stoneflies near water, it is wise to use a dry fly that matches the size and color of the natural insect. The wings should be slightly longer than the body of the fly.

 

Stoneflies fly with their bodies nearly vertical; this is especially true of the females because the extra weight of their precious eggs forces them to fly in a vertical position. During their fluttering flights, the females touch the surface of the water and deposit their eggs. We became interested in observing the egg-laying flight of a female stonefly, and conducted an interesting experiment. We captured a large Perla bipunctata, and placed the insect in a glass tank containing just a few liters of water. The stonefly flew from side to side in the tank, touching the surface of the water and depositing its eggs; we could actually see the small black clusters of eggs drift to the bottom of the tank.

In nature, the eggs hatch into small larvae within three to four weeks. As we have already stated, the nymphs live for one to three years before hatching into adults. And finally, depending upon the species, the adults have life spans ranging from a few days to three months.

Except for a few outstanding examples, adult stoneflies are not so important as hatching mayflies and caddisflies. But the nymphs are extremely important to successful fly fishing. The nymphs are present throughout the season, and the trout are used to seeing and feeding on them. Stonefly nymphs are also fairly large, so they are easy targets for the trout.

Let us show you how to tie one of our favorite stonefly nymph patterns. It has many realistic features, yet is fairly easy to make. This pattern will work wherever you find trout living in clean, flowing water.
__________________

Igor and Nadica Stancev have become regular contributors to our magazine. Their wonderful photos of insects and creative flies always amaze us. Igor and Nadica live in Macedonia.



Nadica’s Stonefly Nymph
Hook: Tiemco TMC200R, sizes 10 to 4.
Head: Gold or brass bead.
Thread: Cream 6/0 (140 denier).
Weight: Lead wire.
Butt: A fine, flashy dubbing such as Wapsi Fly’s Super
   Bright Dubbing, but you may substitute your
   favorite brand of fine-fibered dubbing. Common Antron
   dubbing is an excellent choice.
Tails: Stripped hen or cock body quills.
Abdomen: 4-millimeter-wide latex strip such as Hareline
   Dubbin’s Nymph Stretch Skin.
Wing cases: Brown partridge, hen, or grouse feathers.
Thorax: Rabbit dubbing guard hairs. Brush out the 
   underfur before placing the remaining material in the
   dubbing loop.

 

Starting Danica's Stonefly Nymph
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1. Slip the bead onto the hook with the small hole facing the hook eye. Place the hook in the vise and start the thread.
2. Place the lead wire on the side of the hook shank. Push the end of the wire into the hole in the bead. Tightly wrap the thread to lock the wire to the hook. Clip the end of the wire at an angle.
3. Wrap the thread back to the bead. Tie a second piece of wire to the other side of the hook shank. Cut the end of the wire at an angle.
4. Spin a pinch of fine dubbing on the thread. Wrap the dubbing around the end of the hook shank. This small ball of dubbing will separate the tails of the fly.


Building the Abdomen
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1. Strip the fibers from two hen or cock body feathers. Tie the bare quills to the end of the hook; use the tapered sections of the quills to mimic tapered stonefly tails. Clip the tails to length; the completed tails should almost equal the length of the abdomen.
2. Clip the end of the latex strip at an angle. Tie the tip of the strip to the base of the tails.
3. Wrap the latex strip up the hook to form the abdomen; each new wrap should slightly overlap the previous wrap. Tie off and clip the excess strip. Next, apply a thin layer of cement to the backsides of two partridge feathers. Allow the cement to dry, and clip the feathers into heart-shaped wing cases.
4. Tie the first wing case to the hook in front of the abdomen. Make a dubbing loop and prepare to complete the fly.



Finishing the Fly

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1. Brush the underfur from a pinch of rabbit dubbing. Fill the dubbing loop with the remaining guard hairs. Spin the loop closed. Gently lift the wing case, and make two wraps of dubbing behind the case.
2. Continue wrapping the dubbing up the hook to complete the thorax of the fly; brush the guard hairs back while you work. Tie off and clip any remaining dubbing loop.
3. Brush the guard hairs down the sides of the fly. Tie on the front wing case behind the bead head. Tie off and clip the thread.
4. Color the abdomen using a dark brown permanent marker. Stroke the pen from the head toward the tail of the fly to maintain the segmentation. There, our finished fly looks great!

 
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