Understanding Caddisflies
If you look at a typical trout stream hatch chart, you will probably see caddisflies listed as
a black one, a brown one and maybe even as an "elk hair" caddis, even though it is a fly
pattern, not a caddisfly species. If you look at any anglers fly box, you may see one or
two adult caddisfly imitations hidden among many mayfly imitations. If you study the food
that trout eat, you will discover that they eat at least as many caddisflies as they do
mayflies, maybe more. Why then are caddisfly imitations so under utilized and why are
caddisflies so under rated as a trout food?

Of the fifteen families and over seven hundred species of caddisflies that are important to
anglers, the
Hydropsyche and Ceratopsyche or spotted sedges, or cinnamon sedges as
they are sometimes called, represent at least half of the caddisflies available to trout.
These two genera are so similar that entomologist only recently classified them into
separate categories. They are so similar that the imitations will work for each of the
stages of life for these caddisflies.

In the same family are the "little sister" or
Cheumatopsyche caddisflies. These are almost
the same as the spotted sedges, just a hook size smaller and a different color. Together
these three genera probably represent sixty percent or more of all the caddisflies
available for trout to eat.  

These are net spinners. Their larvae do not build cases, rather they reside in shelters
that they enter and exit on a silk line to eat plankton caught in their nets.  Plankton is the
key. Generally speaking, the more plankton a stream has the more net spinning
caddisflies the stream has. It is easy to tell how much plankton a stream has. If you slip
on the rocks when wading, it probably has a lot of plankton.

During the time the caddisflies exist in the pupae stage of life, which is usually about a
week, they are available for trout to eat.  They remain on the bottom until the time they
begin to emerge into adults. Then the helpless pupae drift for several yards, even
hundreds of yards, before emerging. During this time trout can pick them off with ease.
As soon as they become adults with dry wings, they quickly depart the water. Trout do
not need to expend any energy or effort trying to catch the adults. The pupae were
readily available throughout the water from the bottom to the surface for a relatively long
period of time.

There are many other species of caddisflies that build cases. Some of these are eaten
larva, case and all. Most of the case builders, like the net spinners, are much more
readily available to trout as a pupa than an adult.

After they hatch, the adult caddisflies usually live for up too a month or so and are not
available for trout to eat until they return to the water to deposit their eggs, die in or fall
spent on the water.  So, when an angler notices large numbers of caddisflies in bushes
or swarms, the major part of the hatch is usually over. In other words the angler has
already missed the best fishing opportunity.  Unfortunately, this is the time many anglers
attempt to catch trout on their dry caddisfly imitations.

After the adults mate the females deposit their eggs in the water in one of three different
ways - by crawling down the stems of plants, the bank or rocks; diving and pasting their
eggs on the substrate; or dipping their abdomens in the water or just landing on the
water and depositing them. Sometimes, depending on the particular specie, they deposit
their eggs using a combination of these methods. At this time you can catch trout on an
imitation of the adult but with most species this event usually occurs very late in the day
or at nighttime. In other words, unless you want to fish very late or at night, in most cases,
your opportunity of catching trout is over when the hatch is over.  

Like everything else to do with fishing, there are exceptions. The
Brachycentrus genus,
called the "Mothers Day" hatch in the West and just "black caddis" in the East, offer
excellent fishing opportunities for trout during the day. These early season hatches
usually occur in the morning and the adult females usually deposit their eggs on the
surface of the water during the afternoons. Both events can even occur at the same time.
This popular hatch is usually confined to a couple of weeks or less than a month.
The only way for an angler to be able to consistently catch fish on caddisflies is for them
to learn the habits and habitat of the species of caddisflies present on the stream they
are fishing. This is necessary in order for one to effectively imitate the behavior of
caddisflies and to fool the trout into thinking their imitation is the real thing, so lets get

Caddisflies, or trichoptera, are the least understood aquatic insects found on trout
waters. Most anglers simply cannot recognize a caddis hatch until, in many instances; it is
already to late to do them any good. Many do not even attempt to do so, thinking that
mayflies are the only important hatches to concern themselves with. Unlike mayflies,
caddisflies do not change from the dun stage to a spinner stage. It is not easy to
determine whether the caddisflies are emerging or departing the water from the
underwater egg laying process that some species exhibit. At this point, you may be
wondering what difference that would even make.

When emerging, most species of caddisfly pupae swim from near the bottom to the
surface skim, shed their shucks and quickly become airborne. When in the underwater
egg laying process, some species of full-grown caddisflies dive or swim to the bottom,
deposit their eggs, return to the surface and, in many cases, depart the water looking
very similar to emerging caddisflies. Not only was their action and behavior beneath the
water entirely different from the emerging caddisflies, their appearance beneath the
water was entirely different. Caddisfly pupae ascending to the surface do not resemble
egg laying females that are returning to the surface. You may not recognize the
difference when they depart the water, but rest assured that trout will have no problem
detecting the difference in what they may be keying in on, maybe even selectively. In
other words, you may not know whether to fish a pupa imitation of an emerging caddisfly
or a wet fly imitation of an egg layer in this case.

Another common deception that frequently occurs, is that when some species of
caddisflies emerge, they reach the surface skim and their wings pop out of the wing case
already dry. These caddisflies leave the water in seconds. They do not stay on the
surface. The trout know this. They can observe the activity and they don't waste time and
energy trying to eat an adult when they only have split seconds in which to do so. They
can take an emerger, much, much easier and they do. On the other hand, anglers see
the adults leaving the water, as well as flying around over the stream and bank, and
immediately tie on a dry fly. They do not get good results and just assume the trout are
not taking caddisflies. This is probably the single largest reason many anglers do not
succeed in fishing caddis imitations.  

Other species of caddisflies crawl on the bottom to shore or rocks that protrude out of the
water before emerging. Others swim to the surface and walk on the film to shore before
emerging. In both of these cases, an entirely different means of presentation and
imitation is needed.

To farther complicate matters, often times when large swarms or clouds of caddisflies
appear over the water, they are neither females laying eggs or emerging. They are males
congregating together. It is common for anglers to waste their time fishing caddis patterns
during this activity when the caddisflies are actually not available for the trout to eat.
Determining the stage of a caddisfly hatch is of utmost importance if you are going to
imitate the naturals effectively.

Hatch charts that are suppose to assist anglers visiting new streams may be of little help
when it comes to caddisflies. Often hatch charts list “caddis” just as if it were an individual
species of insect even thought the same hatch chart might list a dozen species of
mayflies for the same stream. Others hatch charts may merely list them by different
shades of color. This, of course, may help in that it at least tells you that some species of
caddisfly is going to hatch, a gray one, dark one, or black one, but it offers very little
other information - information that is critical in knowing how to imitate the various families
of caddisflies. Knowing the behavior of the particular family and sometimes, genera and
in a few cases, even the species of caddisflies that you are imitating, is just as important,
if not more important, than knowing what color and size of fly to use.   

Studies have shown that caddisflies are a major part of the trout’s diet, yet compared to
the level of attention that mayflies receive, one may get the feeling that they are being
overlooked. In the Midwest, for example, it is thought by many that caddisflies represent
not only a good portion but also the majority of the trout’s food supply.
There are eighteen families and over twelve hundred and sixty species of caddisflies in
North America. Caddis larvae range in size from the micro caddis of about an eight of an
inch long up to over two inches long. Adults can be as small as one-sixteenth of an inch
long up to an inch and one-half in length.

Those anglers that are familiar with the various genera of caddisflies; know how to
recognize and match the insects at the various stages of a hatch; and present imitations
that properly imitate their behavior are going to catch a lot more trout than those that do
not. Recognizing and identifying the various species is not an easy task, even for
professional entomologists. Fortunately, it is not a definite requirement for anglers,
although being familiar with some of the major species certainly doesn’t hurt anything.
One reason many anglers ignore caddisflies is that they associate them only with low light
conditions. Much of the activity of some species does occur at night. However, most of
the activity anglers should be concerned with occurs either very early in the mornings or
late in the day, especially on clear, bright, sun shiny days. In other words, many anglers
haven’t gotten out of bed or they are already having dinner when most caddisfly activity
on the water occurs.

There is another prime reason for the lack of attention that caddisflies get from anglers.
There is not much difference in the shape of the various species in the full, grown adult
stage of life, and with many species, little variation in their colors insofar as the complete
color spectrum is concerned. Most caddisfly imitations are simply different sizes and
shades of color of the same thing. While this may not be far from accurate in many cases
where only the adult is being imitated, such a generalized approached doesn’t begin to
imitate the caddisfly species at the larvae and pupae stages of their life. The colors and
shapes of the larvae and pupae from specie to specie can vary more, than the full-grown

The adult caddisfly may well be the least important stage of life that we need to be
concerned with. Most of the life of most species of caddisflies, as much as several
months, is spent as a larva, compared to only a few weeks for both its pupa and adult
stages of life.

The larva is in the water for most of the year whereas the full grown adult is actually out
of the water, unavailable for the trout to eat, most of its lifetime. It is true that much of the
time larvae, cased and non-cased, are hidden, under rocks and out of view of trout, but
all in all, they are much more available for trout to eat than the full-grown adults. The
adult is usually available only for a few seconds while it emerges from its pupa shuck and
later, only for a very short time as an egg-layer, if at all, depending upon the specie.
During a hatch, in most cases depending upon the specie, there are far more emerging
pupae eaten by trout than adults. This means that what most anglers have in their fly
boxes to imitate caddisflies - usually only dry adult imitations, actually imitates caddisflies
while they are on the water for only for a few moments of their entire life.

There are two basic types of caddis larvae, the free living and the case-building larvae.
Although trout readily eat cased caddis larvae, case and all, there are few patterns to
match the many types of the case-building larvae.

The cases are built of various types of leaves, sticks, small stones, sand and other
similar things, depending on the species of caddisfly. This is why those who check will
find such material in the stomachs of trout.

There are times during the growth of the larvae when they shed their cases to built larger
ones. The larvae are very exposed and available for trout to eat during these periods of
time, yet there are few patterns to imitate the cased caddis when they are out of their

There are also relatively few imitative fly patterns of the worm-like, free-living larvae or
the net spinners that hang on the end of their silk line readily available for trout to eat.
The larvae of free-living caddis live on the bottom. They constantly move along the
bottom feeding. They do not swim but do move about in the current if they become
dislodged. They are subject to being eaten by a trout most of the time. The net spinner
species built nets outside their permanently attached cases to catch their food. This
makes them easy prey for the trout much of the time.

In many streams, the free living larvae, as well as the net spinners, are a major source of
food for trout. The most popular of these free-living larvae is the green rockworm, which
is normally found in riffles and oxygenated water. They prefer rocky bottoms to weedy,
soil based bottoms.

There is also what is called a “behavioral drift” that many species exhibit, where the
larvae just drift with the currents during the night until dawn. The peak times of the
behavioral drift, according to those that have taken stream samples, are just before and
after dark, and again just before and after daylight. Trout eat many caddisfly larvae
during these times. The fact is, in most waters, trout can take some specie of caddisfly
larvae just about anytime and most of them are generally available for a total of about
eight months or more of the year.

When the larva matures and becomes ready to change into a pupa, it seals it case, or
builds one if it is a free-living or net building larva, and grows wings inside a thin covering
called a shuck.   Once it converts into a full grown fly inside the shuck, it frees itself from
the case. Caddis pupae usually drift along the bottom until the time comes for them to
emerge. At that time, pupae will ascent to just beneath the surface using their legs to
swim. They may drift just under the surface film for a short time or immediately shoot up
through the water to the surface. This stage of life, the pupa stage, usually last from one
to four weeks.

The pupae of most species swim to the surface to hatch, although some species crawl,
float or walk to the banks to emerge. These different forms of caddis pupae may drift for
some time and take some time to hatch, but normally, when they do, the full-grown fly
leaves the surface of the water very quickly. Sometimes they may take a hop, skip or
jump before leaving, but it usually happens quickly and trout have a very short window of
opportunity to get the adult fly. Not all of them make it out of their shucks. In certain types
of calmer water, some of them may be unable to make it through the surface film. Trout
can be taken on patterns that represent these “cripples” or flies that don’t make it off the
surface of the water.

The average time for the adult caddisfly to live, if there is such a thing, is about a month.
Most of the time they are living in the shade of brushes, trees and streamside vegetation.
During this time they mate, lay their eggs and die. One reason caddisflies can live
onshore for extended periods of time, incidentally, is that they are capable of drinking

You may witness very large numbers of caddisflies in the air over the water and
sometimes on the banks. This may go on for some time during the day until they are
ready to lay their eggs. This is yet another thing that makes identifying the stage of
caddisfly activity difficult. You commonly may see large numbers of caddisflies flying,
even darting about near the surface of the water, when they are neither emerging nor
laying eggs. Often anglers fish adult imitations when in reality, they are just wasting time.
Some of the caddisflies that lay their eggs on the surface of the water bounce up and
down across the surface actually touching the surface of the water to assist in releasing
their eggs. This fluttering type of activity attracts the trout although the caddis flies are
flying most of the time and not actually on the water. The trout may tend to move about
looking for a meal during this time.

Other species of caddisflies that lay their eggs on the surface just drop their eggs and fall
to the surface doing nothing but maybe fluttering a time or two before they die. Then
there are those species, and there are a lot of them, that do not deposit their eggs on the
surface, rather dive or crawl to the bottom and deposit them. The divers can start high
above the water and literally nose dive in and swim to the bottom. When this duty is over,
they either return to the surface to fly away or, if their life’s duty is finished, just drift away
with the currents.

Some species of caddisflies mate and lay their eggs more than once, as many as two,
three or even more times. When they do complete their duties and drift on the surface of
the water dying, they are of course, very susceptible to being eaten by trout. This “spent”
wing shape or silhouette of the fly with its wings spread should be imitated with a different
pattern than that of the regular adult.

Again, most of the time during a caddis hatch, you could probably catch some trout using
just one type of fly that represents the larva. At the right time, however, you should do
much better fishing a pupa imitation.  You may even do well at times using only the very
popular elk hair caddis of the right size but don ‘t always count on it.  For sure, however,
you would consistently catch more fish if you closely matched their larvae, pupae and
adult stages including the egg-laying adults in some cases. More importantly, is that you
would be much more successful if you presented the various flies matching those stages
of the life cycle in such a way as to imitate their behavior.

You may get by with a typical caddis fly imitation of the right size if the color is close, but
you may not catch anything if you are presenting the wrong type of imitation; larva, pupa
or full grown fly, for the current stage of activity. Determining what stage of activity is
occurring is not always easy. In fact, as we previously said, determining whether or not
trout are feeding on caddisflies, is usually not easy. About the best clue you have that
trout are feeding on caddis is that when you see trout feeding or rising but don’t see any
bugs. This may indicates that they are feeding on emerging pupae. Even if you get the
stage matched correctly, you need to know how to properly present it to imitate the
behavior that occurs at that stage of life of that particular genera or species of caddisfly.
The purpose of this presentation is to provide the information you need to identify
caddisflies; determine if a hatch is occurring or about to occur; and if so, determine the
status of the hatch in order that you can match the current stage of caddisfly activity with
an imitation and presentation as close to the natural as possible.

Unlike mayflies, certain species of caddisflies can hatch over a period of weeks, even
months. Although the activity varies considerable, peak times will occur during this time
span. The optional “Digital Hatch Guides” show these hatch periods for most all of the
popular trout streams in the U. S. and recommends patterns to match each stage of the
hatch and egg laying process. The optional “Perfect Fly” series will show you how to tie
imitations that match of all species or genera of caddisflies in all of the stages that you
may need to imitate.  

You should be aware that the colors of the caddisflies may vary somewhat, not only from
region to region, but from stream to stream. Their habitat, or chemical composition of the
water and stream bed, can vary the their exact color. You should also note that when
caddisflies first hatch they are usually lighter than they will be soon afterwards. This
means that if you are matching adults that have just emerged, you should use lighter
shades of colors for your imitations than you would for the egg laying adults. When you
see airborne caddisflies, they tend to look lighter than they do when you see them up
close on vegetation or holding them in your hand. Their wings are somewhat translucent
and when you view them with their wings folded, you are in effect seeing the color the
body through the wings.

It is also important to note that the adult males are almost always smaller than the
females, an average of one hook size. Also, you should be aware that the larvae of most
species go through five instars or stages of growth. During the year they become larger
as they grow near the stage that they become pupae. If you have any question about the
size of an imitation of the adult, pupa or larva of a caddisfly, use the smaller size imitation
you are considering.  Staying on the smaller side is usually not as big of a mistake as
using too large of an imitation.

As I said, there are hundreds of species of caddisflies found within the U. S. Some
families contain more than fifty genera. Some genera include more than fifty species. Of
the all the species of caddisflies, only certain genera are found to exist in cold waters that
support trout. Of these, the
Brachycentrus and Hydropsychidae families probably
represent over half of those that are most prevalent on most trout waters for any
significant time.

In some cases, species within a genus look quite different from other species in the same
genus. In some cases, species within the same genus emerge and lay their eggs in
entirely different ways. In those cases, it is necessary to identify the caddisfly by specie
and distinguish those differences in order that you can best imitate the appearance and
behavior of the natural.

In many cases, however, species within the same genus look and act very similarly and in
those cases, being able to identify the insects to the genus level is all that we need to be
concerned with. The same flies and methods of presentation will work for all of the
species within the genus.       
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