|....................... .................... ...Fly Fishing Yellowstone National Park
New KISS Bug Series - Part 8
Some Other Aquatic Insects of Yellowstone
Craneflies are fairly abundant in the park's streams. Craneflies are two-winged insects like
midges, but they are much larger than midges. The larvae look like short, fat worms. There are two
types as far as their preference for habitat. Some species of them live underwater in woody
debris, algae, and aquatic vegetation. Most of them live in the damp soil above the waterline.
The terrestrial type do get into the water. Heavy rain is usually the reason. An imitation of a cranefly
larva is sometimes a fly to use after the streams are swollen from rains. Trout will also eat the adult
craneflies. They are usually in very shallow water and trout mostly feed on them near dusk. You will
find lots of them on some streams in the mid to late Summer.
Interestingly, most of the time I spot a large number of dragonflies in the park, they are eating
mayflies, caddisflies or midges. You will see them dive down from high in the air and grab a small
mayfly. Dragonflies prefer still or slow moving water.
Dragonflies are found more often in still or slow moving water. They are basically a still water
insect but are also commonly found on streams. Their larva are big and trout do eat them. You'all
find the Firehole and Madison River has plenty but so does many other streams in the park. All of
the lake have good population of dragonflies.
Like the dragonfly, damselflies are plentiful in the park in certain types of streams and all the
lakes. They prefer still to slow moving water. The insects have a preference for vegetation with
long stems. That's where they hide to catch the food they eat. They eat mayfly nymphs, scuds and
midge larvae and pupae.
Fish eat the nymphs throughout the season but the best time to catch them on the damselfly nymph
imitation is when they first begin to hatch. When the nymphs begin to hatch into an adult they swim
to the shore beneath the surface of the water. They usually swim within a few inches of the surface,
not in the deeper water. This makes it easy for anglers to imitate them.
The Water Boatman are mostly found in the still waters of Yellowstone. They are most important
during in the late spring when the water first becomes fishable and in the fall when mating and egg
laying takes place. These insects actually breath air. They can trap bubbles which is what give
them a flashy look or appearance at times. That is one reason they are found in the shallows
especially where there's a lot of vegetation.
In the fall, usually late fall, these insects mate and fly over and crash into the water. They dive all the
way to the bottom and paste their eggs on the bottom or stems of plants. They must come back to
the surface for air so they make the trip all the way down and back up. The trout become well
aware of this procedure because they key in on the water boatman when this happens.
Copyright 2012 James Marsh