Western Green Drake
Introduction
This
hatch occurs in our area on the Yellowstone
River, Boulder
River, Madison
River, and many other streams during
the Middle of June and through July. Hatches can be very localized
but they are rarely heavy, if you see a few Green Drakes it's
a good idea to try a corresponding pattern. Drunella
grandis is about
a size #10 or #12 and is unmistakable with its thick thorax - we
jokingly refer to it as the linebacker of the Mayflies. They hatch
in larger numbers on cloudy, overcast days.
Nymph Stage
D. grandis is a crawler mayfly, meaing it crawls along the rocks searching for food and haning on for dear life against the current. The have strong legs, but occasionally are swept away by surging currents. In the nymph stage the mayfiies live for up to a year developing underneath the waters surface. As nymphs they feed on algae, plankton and drifting detritus. They range in size up to about a #10 to #12 hook and are best imitated with Pheasant Tails, Sawyer Nymphs and other dark bodied nymph patterns.
Emergence to Adult
As the time of emergence draws closer the nymphs begin to rise up from the rocks underneath the waters surface. This occurs as a gas bubble forms inside the exoskeletion of the nymph. Turning over a few rocks along the banks will reveal numerous insects underneath with dark wing cases. Fishing a slightly weighted dark Hare's Ear emerger (size #10 to #12) can produce some excellent fish as they are extremely vulneralbe in this stage. Splashy rises often indicate trout taking this emerging mayfly.
Adults & Egg Layers
Adult
Western Green Drakes (size #10 to #12) have very short life spans
as adults most rarely live more than 24 hours. Right after emergence
they float on the surface of the water drying out their wings - which
can take a long time for these big mayflies. They are easlily identified
by their upright wings which resemble a sailboat mast and thick thorax.
During more humid days this may take several hundred yards before
they are dry enought to fly off the surface of the water. Looking
in the tail outs of long runs often reveals trout eating these dry
flies or Duns. After the Duns leave the waters surface the molt to
a spinner stage identified by their now clear wings (with some slight
dark banding in this species). They then mate and lay their eggs
above the surface of the water. Most times they are so exhausted
they fall to the water and again are an easy meal for trout. These
are well imitated with a Harrop Last Chance Cripple, Parachute
Hare's Ear, or Green Drake Wulff in size #10 or #12.
Spinners
I have rarely had good spinner fishing with Green Drakes however it can occur in localized waters so as always be patient and make sure to observe before you start casting.