Importance as Trout Food:
In spite of the quantity of stoneflies in a trout stream, they are not the most important
trout food available to the trout because of the word "available". They are not usually
available. They are usually hidden down between and beneath the rocks and stones that
make up the streams substrate. When they feed, in some situations; when they molt, in
some situations; and when they hatch in all situations, they are available for the trout to
Occasionally, stonefly nymphs get accidentally caught by the streams current and tumble
downstream. Some, mostly the small species, are a part in the behavioral drift. It is
certainly possible to catch trout on an imitation of the nymph at times other than the
hatch but may, on the average, produce less than satisfactory results.
Stoneflies hatch out of the water, not in the water like most other aquatic insects. Most all
stoneflies crawl to the shoreline, rocks or other objects that are protruding out of the
water to hatch. It is during this migration that they are most available the trout to eat.
Imitating the Hatch. You should imitate this behavior by retrieving your nymph imitation on
the bottom towards the bank. Fishing from the bank and retrieving your fly back to shore
is usually more effective than the typical nymphing on the swing and high sticking type
methods are. Keep in mind that the stoneflies move to the quitter water along the shore
or pockets where rocks extend out of the water as opposed to crawling out of fast water.
You want to fish the calmer portion of the water that is adjacent to the fast water in which
the stoneflies live.
Stoneflies live for a relatively long time out of the water. The mate out of the water. Unlike
mayflies, for example, stoneflies can eat and drink as adults. Just because you find a lot
of stoneflies in the bushes and trees along the banks of a stream does not necessarily
mean you can catch trout on an imitation of the adult. The only time the adults are going
to be available for the trout to eat is when the females are depositing their eggs.
Most stoneflies deposit their eggs during the night but some species do so during the
daylight hours. All of them prefer to deposit their eggs during low light conditions.
Overcast skies and rainy days may offer some opportunities for anglers to catch trout on
There are nine families of stoneflies in the United States. All nine families are found in the
park's streams. Unlike caddisflies and mayflies it is usually not necessary to determine
these to any level below the family level. With only a very few exceptions, there is very
little difference in the genera of the families. Most all of them are about the same size and
shape. The colors of the nymphs and the adults within a family can vary some within the
family. The best way to choose a fly to match them in the event you are unable to identify
a hatch is to catch one of the adults and match it. If you have our stonefly patterns then
you would have a fly to match them. You can find the adults by checking the bushes,
trees and grass along the stream side for the stoneflies. The nymphs are also easy to
acquire. They can be found clinging to the bottom of stones. Normally, you can pick up
the stones from the bottom of the stream.
Little Brown or Black Snowflies
This family of stoneflies may be observed during the winter months. They represent one
of the few species of aquatic insects that emerge and is available to the trout when the
water is extremely cold. Although these are classified as "Little Brown Stoneflies" for the
most part, they are black. Most anglers refer to them as "Little Blacks" and some as "Little
Trout can be taken on nymph imitations of the Snowflies but imitations of the adults are
rarely productive. Trout are not very prone to rise to the surface to eat the egg laying
females on the surface in the very cold water that usually exist when they hatch.
Little Brown or Black Needleflies:
This family of stoneflies are most plentiful in the late summer and fall months of the year.
They are abundant up until very cold weather occurs. They can usually be found during
the months of August through December.
Many anglers confuse these small stoneflies with caddisflies because in the air they look
like brown caddisfleis. They look much larger flying than they actually are. They are easy
to identify because they are the only stoneflies that are slim, long and shaped like
needles. They have wings that roll around their bodies rather than lie flat on the top of
They deposit their eggs during the daylight hours as well as after dark and trout can be
taken on flies that imitate the egg laying adults. Late afternoons provide the best
Little Brown or Black Forestflies
Little Brown or Black Winter Stoneflies:
Both of these families are both brown and black and all shades in between. Both families
are so similar that anglers do not need to be able to differentiate between them. The
minute differences are only important to entomologist and can only be determined with
magnification. Species of both families hatch during the winter or early springs months
and usually do so in fair to large quantities.
Imitations of the nymphs work very well just prior to and during a hatch. Some of the
adults can usually be found depositing their eggs before dark. Fish can be taken on the
adult patterns during this time but is not a totally reliable method of fishing. You will find
several different species of Little Black and Little Brown Stoneflies. This can be confusing
to those that pay close attention to it. Technically, there is no such thing as a Little Black
Stonefly. They are all Little Brown Stoneflies. Anglers call them Little Black Stoneflies
because they are just that-Little Black colored stonefles. So the bottom line is that it
makes no difference. You should match the size and color. We are only pointing this out
for those weekend entomologist that are ready to call our attention to what they would
call an error.
Little Green Stoneflies:
The "Little Green" stoneflies hatch in the summer after many other species have already
hatched. These are usually small stoneflies. The adults of several of the species in this
family are yellow and can easily be confused with the "Little Yellow" stoneflies but this is
not important as long as anglers correctly match the size and color.
Species of the "Golden Stonefly" family are one of the most plentiful group of stoneflies.
Most of these are very colorful as nymphs. Patterns of dark brown and yellow distinguish
them, especially those that are near maturity. The adults range from a golden dull yellow
color to a solid brown depending on the species. Imitations of the nymphs can be very
productive prior to a hatch. Most of the egg laying activity occurs after dark but late
afternoons may produce some activity especially if low light conditions exist.
Little Yellow Stoneflies
Species of the Isoperla genus of the Perlodidae family are usually called the " Yellow
Sally" but several other species are also called Yellow Sallies, so that depends on what
part of the country you are in. It seems most anglers call any of the Little Yellow
Stoneflies a "Yellow Sally". The Perlodidae family is one of two families that make up the
Little Yellow Stonefly group and are among the most plentiful groups of stoneflies.
These stoneflies usually hatch in the afternoons and usually begin to deposit their eggs
late in the afternoon prior to dark and continue to do for some time in the evening. This
makes it productive in most cases to imitate the egg laying activity before dark.
Peltoperlidae (Roach Flies):
Little Yellow-Summer Stone
The Peltoperlidae family, called Roach Flies, are also little yellow stoneflies. They are not
usually as plentiful as the Perlodidae family. We have not experienced these in
sufficient enough quantities to cause selective feeding but we have found many of the
adults and nymphs in several streams. Although they are shaped slightly different (more
like roaches) other imitations would probably suffice to imitate them should you find them
The giant black stoneflies are plentiful in most all of the streams in the east. The
Pteronarcys dorsata is the most common species in most eastern streams. The
salmonflies, such as the Pteronarcys californica, are plentiful in many western trout
streams. These are huge nymphs that live for 3 or 4 years. Trout can be taken on
imitations of the large nymphs during the day during the hatch period, even though most
of the Giant Stoneflies hatch during the evenings.
Imitations of the adults fished during the day are rarely effective. These giant stoneflies
hatch during the night. Imitating the adults is not effective unless you fish at night and
that is difficult to do effectively in most of the streams. Adult patterns presented at the
end of the runs and heads of the pools may be effective if fished early in the morning just
Since the families of the larger stoneflies (the Goldens and the Giants) live for 2 or 3
years, they are always in the streams in all sizes. They are definitely a very important
and abundant trout food. It is true most of them stay hidden most of the time. Only a few
small species have been found in a drift.
Trout may have a hard time finding one to eat unless it is trying to crawl to a bank to
hatch, or the stonefly nymph gets careless feeding at night. There is one thing you can
count on, however. The trout know they are there and they are ready and willing to
pounce on one whenever they get the opportunity. .
Copyright 2013 James Marsh
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