Sedges
are the aquatic cousins to butterflies and moths. Indeed the adult sedge
looks much like a moth except that it doesn't have the scaly wings or
the siphon tube of the moth. Many names, such as hellgrammite, are erroneously
applied to the sedge. I grew up using the term sedge as opposed to Caddis
and will use that for these discussions.
Life Cycle:
Sedges
go through the egg, larva, pupa and adult stages. Adult mating usually
occurs on the ground or among shoreline vegetation. After fertilization
the female skims over the lake surface depositing eggs. The eggs are
often bright green in color and are usually laid in strands. The eggs
sink to the bottom, hatch into larva, and the young larva then form
their cocoon-like casings. The larva grows within it's casing which
is remade or enlarged about 5 times before the larva pupates. About
three weeks prior to emergence, the larva seals the entrance to the
casing and pupates within. When developed the pupa breaks the seal,
crawls out, swims to the surface and hatches into an adult. Pupal skins
are often seen floating on the surface. Adults live from two weeks to
two months. Most sedges have one or two generations per year but some
of the larger species take two years to complete a generation.
Appearance:
The larva
are grub-like in appearance and hide within their protective casings.
The larva make their casings by binding together small rocks, twigs,
leaves or other material. The materials and design of this casing can
be used to determine the species of sedge. Within the casing the larva
pupates and when developed, the pupa looks much like the adult but with
under-developed wings. It has longish legs and antenna and a well-developed
abdomen. The abdomen usually has eight segments and a row of gills along
the sides and on many species the abdomen is wider at the posterior
than near the thorax. With the smallish thorax, this gives the pupa
a somewhat pyramidal shape. Adults are much like the pupa but with fully
developed wings. The wings give the adult an even more pyramidal shape
than the pupa. Some adults have wings that are transparent.
Size:
The adults
of larger sedge species will get up to about 30 mm (1.25 inches) in
length while some of the smaller relatives will not exceed 6 or 7 mm
(1/4 inch). On most of the interior lakes they average 12 to 18 mm (1/2
to 3/4 inch). Pupa are pretty much the same body size as the adults.
Colour:
The larva
has a dark head with an abdomen that is generally cream colored to light
green within the casing. The pupa is commonly a dirty or khaki green
to a very bright green and various shades of brown are not uncommon.
Adults generally have a greenish body with a mottled grayish color to
the wings (like many moths). Some species have semi-transparent wings
and these are often tan to reddish brown in color.
Movement:
Larva
slowly crawls along the lake bottom carrying their portable casing.
After the sedge pupates, the pupa crawls out of it's casing and may
immediately swim to the surface or spend some time on the lake bottom
depending on it's readiness for adulthood. At the surface the pupa breaks
the water surface tension and is stationary for a couple of minutes
while the adult breaks opens the pupal shell and hatches and dries its
wings prior to taking flight. After mating, the adult female is back
on the lake and skimming over the water surface while she lays her eggs.
She is actually running on the water surface tension as opposed to flying.
Habitat:
Sedges
are able to withstand a wide variety of water conditions. However, they
seem to prefer shallow, cool, well oxygenated waters. A few sedges are
predacious but most obtain food from Algae, diatoms, plants and animal
materials that have settled to the lake bottom. These foods are more
abundant and available around weed beds than a muddy or sandy bottom.
Sedges are easy prey for the rainbow trout and their populations are
among the first to decrease as trout populations increase. Trout readily
feed on the adult and pupa stages but seldom on the larva since it rarely
leaves its casing.
Importance
to Fly Fishing:
Unknown
to many fly fishers is the fact that the sedge (Caddis) is the third
most important food source for trout in our Interior lakes coming in
at 13% of the total food consumed. The daytime feeding samples show
that 8% of the trout's daytime feed is on sedges. For fish feeding in
the evening or at night the feeding samples rise to 19% of the total
food intake. In terms of a relative ranking this actually places sedges
as the second most important evening or nighttime food source. Only
shrimp are more frequently consumed in the evening hours.
Sedges
are one of the last aquatic bugs to start hatching in the spring and
one of the first to disappear in the fall. This means that during the
time they are available to the trout they are one of the primary foods.
Indeed, from the last week in June until about mid-July they are often
the main food source of the trout.
Larva:
In their
larval stage the sedges are wrapped in their cocoon-like casings and
are not normally found in the feeding samples of trout in our Interior
lakes. However, trout in streams and rivers seem to feed on the larva
more frequently as they become dislodged from the bottom and drift with
the current. For the lake fly fisher the sedge larva is of little importance
for imitating with flies.
Pupa:
When sedges
first become available is the best time to fish the pupa patterns. Often,
at this time of year, the larva has pupated and the pupa has crawled
out of the casing but isn't quite ready to hatch. It will crawl around
the lake bottom as it waits for exactly the right hatching conditions.
They are easy prey at this time and the trout will actively seek them
out. To a lesser extent the same thing is happening throughout the remainder
of the sedge season. pupa.
When the
pupa swim to the surface for hatching they are also easy prey and readily
eaten by the trout. As the sedge pupa leaves the casing and swims to
the surface it is one of the main food sources of the trout. Yet many
fly fishers don't tie sedge pupa patterns and the patterns tied often
don't even look much like a sedge pupa. About one quarter of the flies
in my fly box are sedge pupa patterns of different size and color. I
believe that many fly patterns, even the Half Back and the Doc Spratley,
are often taken by the trout thinking it to be a sedge
Try tying
fly imitations of sedge pupa with 'weighting' at the back of the hook.
Dubbing holds air, gives the
fly sheen and seems to work better than flies tied with yarn or other
material. Give the fly a pyramidal shape with the widest part of the
abdomen over the weighting. The dubbing can be trimmed to get the right
shape. Add a wing case with legs and antenna starting just behind the
eye of the hook and make them about as long as the fly. The eye of the
hook will imitate the head of the pupa. Fish the fly right on the bottom
OR after it has reached bottom give a fairly fast retrieve to bring
it towards the surface. The weighting at the back of the hook will give
it the right angle for approaching the surface when using a dry line
and long leader.
Adult:
Adults
are usually taken while they are hatching and letting their wings dry,
or when they return to the lake for laying eggs. How you present your
fly in each of these circumstances is totally different. When the sedge
is hatching, just let your dry fly sit on the surface and wait. Let
it drift with the wind but don't retrieve it. When the sedge is laying
eggs you will see it 'skimming' over the waters surface. When you see
this skimming, or travelling of sedges, is when you want to retrieve
the dry fly at about the same speed as the actual sedge. In both these
cases the dry fly will work better if there is a breeze or slight wind
as opposed to perfectly calm wind conditions.
The shades
of color in deer hair are fairly representative of the coloration in
Sedge wings. The deer hair is an excellent material for tying flies
to imitate the adult sedge and it floats well. For durability of the
fly, I often tie a 'mouse's ear' type of fly from deer hair and trim
to get the pyramidal shape.
Hatches:
The first
Caddis hatches of the year will vary with elevation but start watching
for them about the last week of May. The numbers and frequency increase
until about the last week of June or first week in July and then steadily
decrease for the remainder of the season. The last of the 'major' hatches
is the Cinnamon Sedge in early September but timing of this hatch is
somewhat dependent on the weather. Hatches often occur in the late afternoon
and evening and many are after dark.
CADDISFLY
(Sedge)
Larva:
Pupa:
the
fly sheen and seems to work better than flies tied with yarn or other
material. Give the fly a pyramidal shape with the widest part of the
abdomen over the weighting. The dubbing can be trimmed to get the right
shape. Add a wing case with legs and antenna starting just behind the
eye of the hook and make them about as long as the fly. The eye of the
hook will imitate the head of the pupa. Fish the fly right on the bottom
OR after it has reached bottom give a fairly fast retrieve to bring
it towards the surface. The weighting at the back of the hook will give
it the right angle for approaching the surface when using a dry line
and long leader.
