Stonefly

Written By: Dick Babine

Jason Neuswanger of troutnut.com and Richard J. Babine of richard@thebabines.com have generously authorized the use of all macro photographs used in this chapter.

Kingdom:	Animalia	(Animals)
Phylum:	Arthropoda	(Arthropods)
Class:	Insecta	(Insects)
Order:	Plecoptera	(Stoneflies)

Your only a Stone’s throw from early or late season success.

Stoneflies are among the largest aquatic insects in any Maine Trout Stream. They can, however, create outstanding fishing opportunities in certain places and at certain times, when fish are not focused on prominent hatches of other much smaller aquatic insects. To most anglers; they are only significant as handy nymphs to imitate when nothing much is hatching.

The best stoneflies for the angler are the gigantic Pteronarcys californica "Salmonflies" of western legend. The large Golden Stones of the Perlidae and Perlodidae families are more common across the country. The smaller Willowflies of Taeniopterygidae are sometimes the first dry-fly insects of the season, and the little yellow or green Chloroperlidae flies are a common sight throughout the New England summer.

March’s creature of the month is the stonefly. The Stone Fly can be an important trout and salmon insect with which the fly fisher should be concerned. It is less important than the Mayfly or the Caddisfly, but anglers should be familiar with this insect and carry several nymphal imitations, which resemble the genus Plecoptera, which means in Latin: pleco-“folded” and ptera- “wings”.

Like the Mayfly, the Stonefly has an incomplete life cycle, by not going through a pupal stage. Only the nymph and adult stages are of importance to the fly angler. However, since the Stonefly emerges while the Caddisfly adult is still in command, little attention is given to the Stonefly nymph over much of the state, again because of the lack of knowledge concerning its use and the proper technique required for consistently being successful in luring strikes.

This insect will make its appearance no later than late June and will last until around the end of July. Stonefly Nymphs require highly oxygenated water that has a medium to fast movement. The other requirement is that the bottom of the river or streambed be consisting of small-to-large rock aggregate. The name Stonefly probably came from where they are found along streams hiding or crawling in and around the rocks and stones.

HATCHING ACTIVITY

The reason for me saying that the stonefly is somewhat unimportant as a primary trout food source is that this insect owes its unimportance to its emergence style, which keeps the stonefly safe from fish at a stage when mayflies and caddisflies are the most vulnerable. Without exception, they emerge by crawling out of the water onto rocks, sticks, or other shoreline objects. In some species the adult emerges from the nymph within inches of the water, and others crawl up to ten feet back into the woods, but this distinction matters little to the trout. After emerging, the adults may live for up to a month. Like caddisflies and unlike mayflies, many stonefly species can eat and drink as adults.

Egg-Laying Activities

Stonefly adults are usually only important when laying their eggs after mating. Some drop their eggs from above the water but many either flutter along the surface or land on the water and create a commotion capable of drawing savage strikes from large trout during midday. They are one reason for the success of the Stimulator dry fly in large sizes.

Nymphal Activities

If stonefly nymphs were mayflies, they would all be classified as "clingers." They have double claws on their tarsi (foot) which helps them grip and scurry over the rocks in fast running waters, and another feature is their flattened bodies create much less resistance in the fast currents making the grasping even easier.

When the emergence of an especially abundant species is near, its nymphs can be so active and concentrated that trout feed on them selectively near the emergence sites.

Although there are many smaller species, most important stonefly species are larger in size. These insects are very poor swimmers, so when they slip or forced from their stony habitats, are very likely caught up in the biological drift and become fair game for opportunistic fish.

This makes stonefly nymph imitations popular and successful during non-hatch periods. Stoneflies, a relatively small group of aquatic insects but do represent the most colorful in nature. Golden Stones, Salmon Stones and the Nasqually Stone represent the largest species. Stoneflies have four wings, which are heavily veined, lying flat over the body until the insect takes flight. Colors will range from bright yellow, misty gray, salmon pink, tan, brown and black.

These stones come off the water in morning to midday and in general are 6-8 mm in size. During the early spring emergence, they are often referred to as “Snow-flies,” and are observed crawling on the snow banks next to their home waters. This activity can occur in early March and continue through May. When this insect hatches, the larvae will crawl out of the water and hatch on land. The evidence of this activity is found along the riverbanks in the form of hundreds and hundreds of empty shucks, attached to rocks, tree trunks, shoreline bushes and any aquatic plant that reaches out from the water.

When and more importantly if you observe this behavior, you know that the fishing later on just before sunset will be well worth the trip. The female will return at night to deposit the eggs into the water. Most females will skim the waters surface to dislodge the eggs from the female’s abdomen. Others will actually crawl to the bottom of the stream and then release their eggs on submerged objects. The males sometimes emerge before the females, and some species actually attract females by beating their abdomen against a hard surface. A responsive female will often return the same signal. Stoneflies unlike the mayfly live as adults from a few days to around a month or more. These insects have very poor flight characteristics and therefore create quite a splashing and fluttering upon the waters surface during egg-laying and for that reason attract the attention of hungry fish.

The real important thing to realize is that this aquatic insect’s life cycle is in some species more than 24 mos. And for that reason, this fly can be used almost year round. The real reason that this fly is useful is that in the early spring and late fall, when the Mayflies and Caddisflies have completed their life cycles, guess what’s still around? So, in short, you can use the Stonefly nymph along with your Bucktails and Streamers for either the early or late season outings.

Maine’s #1 Stonefly

Family:	Taeniopterygidae (Willowflies)
Genus:	Taeniopteryx (Early Black Stoneflies)
Species:	nivalis (Early Black Stonefly)
Common Name:	Little Sepia (Early Black) Stonefly
Nymphal Habitat:	Burrowed in decaying organic debris (Medium to slow Runs or quiet waters)
Nymphal Activity:	January 7 through February 7 and again September 7 through November 7
Emergence:	First batch: February 7 through March 28 then sporadic thru April 10am – 12 noon then come back a week later for mating flights during mid-day
Suggested Imitations:	Nymph: #16 to #18 American Pheasant Tail Adult: #12 to #14 Dancing Stonefly or Sepia Spent-wing Stonefly

These stoneflies feed on decayed organic matter and therefore prefer to burrow themselves into decaying organic debris and found in the quieter sections of the water system. The nymphs are colored in various shades of brown to almost black.

These nymphs are very important for the Maine Angler during the first days and weeks into the season.

Because of their emergent traights, these critters are of little use to the uneducated angler. Remember that almost all important species emerge by migrating to the banking areas to crawl up onto a stone, streamside vegetation, half submerged branches, twigs or whatever else the stonefly can use to get out of the water. Once out of the water the stonefly will go through the last moults and not return to the water again until the females are oviposting. But from the start of the season until well into April and sometimes May, the nymphs are very active along the bottom of the water column.

Tactic:

Tie on a #14 Dancing Stone then a #18 Sawyer’s Pheasant Tail dropper. In fast current, cast down-stream and retrieve by twitching these flies up-stream. In slow currents or eddies, cast down and across then skitter the dry and dropper in front of any rising fish.

Maine’s #2 Stonefly

Family:	Perlodidae (Medium Brown Stoneflies and Yellow Stoneflies)
Genus:	Isoperla (Yellow Sallies)
Species:	signata (Yellow Sally)
Common Name:	Little Yellow Sally
Nymphal Habitat:	Medium to slow runs and pocket water. Where the nymphs feed on live plant matter and algae but as the nymph matures to include other aquatic creatures become the food of choice.
Nymphal Activity:	January 7 through April 28 and again after the initial emergence October 7 through December 28. This species has only a one year life cycle so as with the Mayflies and Caddisflies, you need to consider the emergence period.
Emergence:	May 7 through June 28 then sporadic until August 28 Twilight into night or night until dawn emergence with egg-Laying at night and again just prior to sunrise. The egg mass is black and protected by the female curling her abdomen to her thorax.
Suggested Imitations:	Nymph" #18 Sawyer’s Pheasant Tail Adult: #12 Yellow Stimulator

As with almost all stoneflies, they migrate towards the shore, so you need to cast from shore and retrieve Hand over Hand towards the shoreline.

Maine’s #3 Stonefly

Family:	Chloroperlidae (Little Yellow & Little Green Stoneflies)
Genus:	lloperla (Sallflies)
Species:	imbecilla (Little Green Stoneflies)
Common Name:	Little Green Stonefly
Nymphal Habitat:	Faster Water and feeding on decaying leaves and pine needles
Nymphal Activity:	January 7 through May 14 but migrate downstream from fast water by releasing themselves into the biological drift (Bad Move).
Emergence:	May 14 through July 14 - 2pm until dark but sporadic
Oviposting:	A more concentrated activity that will draw fish
Suggested Imitations:	Nymph: #16 or #18 Bright Green Sawyer’s Pheasant Tail Adult: #16 or #18 Little Green Stonefly

Not all adults are green in color but most are olive green to brownish yellow. The nymphs, however, are very bright chartreuse in color. Oviposting will almost always take place in low light conditions.

These small stoneflies are also very easy to use as a dropper fly. Just tie on the adult imitation and to that attach a dropper nymph. The adult will act as a strike indicator and the attached nymph will act like the emerger. Two for the price of one, what a deal!

Tactic

Tie on a #16 Little Green Stonefly then a Sawyer’s Green Pheasant Tail as a dropper. Twitch up-stream or Skitter down and across.

Maine’s #4 Stonefly

Family:	Pteronarcyidae (Salmonflies)
Genus:	Pteronarcys (Salmonflies)
Species:	dorsata (Salmonfly)
Common Name:	American Salmonfly
Nymphal Habitat:	Fast water Riffles with abundance of decaying organic Matter from which they feed.
Nymphal Activity:	October 7 through April 28 All season as a result of having a three year life cycle. These insects will move up-stream for quite some distance seeking food items.
Emergence:	May 7 – September 21 triggered by length of day and/or repeated days of warm temperatures.
Suggested Imitations:	Nymph: #2 - #8 Kaufmann’s Black Stone Adult: Unimportant due to the insect’s night life.

This is the largest of all stoneflies. The nymphs are very dark, almost a olive brown or just plain black. They can be found just below the riffled areas. These are a late spring offering for most large fish. Dead-drift a large imitation when nothing else seams to work and you might be well surprised.

Maine’s #5 Stonefly

Family:	Perlidae (Golden Stoneflies)
Genus:	Acroneuria (Golden Stoneflies)
Species:	carolinensis (Golden Stonefly)
Common Name:	The Golden Stonefly
Nymphal Habitat:	Medium to fast cool, clean waters that support large healthy populations of caddis as these insects are huge predators.
Nymphal Activity:	October 7 through May 21 These guys are active all year long!
Emergence:	May 28 through July 28
Suggested Imitations:	Nymph: #6 to #10 Kaufmann’s Golden Stone Adult: #4 to #10 Orange Stimulator

As with most stones the emergence activity is to head for the safety of the shore line. This makes the nymph less apt to be a viable food source for most fish. This is usually accomplished at night in order to avoid dehydration caused by the direct sunlight of the day. But, in the coolness of the evening, they will return to lay their eggs on the water’s surface.

Fishing Tips:

Stonefly nymphs are available to fish year round. These nymphs are very poor swimmers and prefer to crawl along the rocks and bottom debris, using their clawed crab-like legs. They eat small invertebrate insects (caddisflies), decaying plant material, organic matter, algae and bacteria. Some are predators and will eat anything smaller than themselves. They can molt their exoskeleton up to 30 times and some species take up to 4 years to develop from egg to adult. They become very active in the spring, just prior to emergence and then again in the fall.

The adults look exactly like the nymphs except that they have folded flat wings over their back when at rest. Quite often they will loose their footing and end up helplessly drifting along with the down-stream current, attracting the attention of the fish.

Remember that fish will often target stones as they migrate towards the edges of the streams and rivers to crawl out of the water during emergence. These large tasty morsels will become very active before the Baetis start acting up, so take advantage of the situation and fish this nymph near any protruding rocks that are located near the stream edge.

In either case the Fly Angler must imitate this action by keeping the fly near or on the bottom, this can be achieved by casting up-stream or up and across and letting the fly sink and tumble with the current along the stream-bottom next to the bankings for maximum effect. Retrieve your imitation by hand over hand toward the stream edge.

Early on, fish a black or reddish-brown nymph, un-weighted, in a size 16-18 swinging it from mid-stream to the bank wet fly style.

Also the female laying eggs will attract fish because of her clumsily making contact with the water in an attempt to deposit the eggs. This is the very time the Dry fly approach is called for: imitating the fluttering, splashing movements of a female stonefly on the water surface will often provoke a violent response from fish.

A tying tip is that Elk Hair Caddis tied in black to reddish-brown will imitate the little Black, Brown, and Rust colored Stones.

If you’re into using droppers, try a stonefly nymph behind an egg pattern. The egg will attract the fish but you will be surprised how many reject the egg and go after the nymph. On your weighted nymph, add the weight 4 to 5 inches above the imitation. This allows the fly to move more naturally and tumble freely in the current.