Mother's Day Caddis Hatch
Introduction
This caddis is also known as the Early Grannom or Brachycentrus
occidentalis (pronounced Brack-ee-sen'-trus ox-uh-den-tay'-lis) and
occurs in mass on the Yellowstone
River from late April to the
start of our spring run off which usually occurs sometime around
the middle of May. This can be one of the largest hatches on
the Yellowstone
River in terms of scheer quantity of insects with
literally millions of insects on the water. During the peak of the
hatch it can be nearly impossible to find your fly line, fly or even
to see the surface of the water.
Larval Stage
The
family of Brachycentridae, of which our Mother's Day Caddis is included,
are tube-case building caddis flies. In their larval form they build
rectangular chimney like casings to protect themselves from their
surrounding environs. These cases are usually made from small aquatic
debris (vegetation). They are most recognizable from the tapered
wood like construction which has a rectangular cross section. During
this part of their life cycle they feed on algae drifting in the
current or scrape it from the surrounding rocks. The larva is bright
greenish in color and usually around a 14 hook size. They often repel
from rock to rock using a silk structure. In turbulent water this
silk can break away causing the larva to float aimlessly in the natural
drift and becoming vunerable to trout predation. A size 14 Glass
House Caddis or Pheasant Tail Nymph accurately imitate this larval
stage of the Mother's Day Caddis.
Emergence to Pupae
As the water temperatures in the rivers approach 54 degrees the
larva start to emerge to a pupae. The pupae swims rapidly to the
suface to emerge as an adult caddis fly. This is the most dangerous
time for our caddis as it can be caught in various currents or have
difficulty breaking through the waters surface. Trout readily feed
on this vunerable stage and is evident
by splashy rise forms usually exposing their dorsal fins or tails
as they turn downward to look for their next target.
Adults & Ovipositors
As
adults our Mother's Day Caddis on the Yellowstone
River are a greyish
tan color with dark veinations evident in the wings (see photo above).
All species of caddis are readily recognized by their tent shaped
wings as they ride along the surface of the water. The females are
a hook size larger than the males and can be imitated with a size
14 hook. The adults can live for several weeks depending on the weather
conditions and will mate in the air or along the willow lined banks
of the river. After mating the female caddis will display a bright
green egg sack on her abdomen. She will then bounce across the suface
of the water dropping her eggs in what is termed ovipositing. Often
time trout will key on these ovipositors and a high floating dry
fly, such as the Troth style Elk Hair Caddis, skated across the surface
will draw agressive strikes.
Spent Adults
After an intense hatch many of the ovipositors will undoubtedly
loose much of their energy and fall spent to the waters surface.
Their wings will be flat on the water which is evident by the loss
of their aforementioned tent shape wings. Trout in calmer stretches
of water may become selective on the spinners so having a few down
winged dry flies in your arsenal is always a good idea.