.......................  .....................    ..Fly Fishing Yellowstone National Park

New KISS Bug Series - Part 3
Bugs 101

Mayflies 101:
Most of you are probably familiar with the life of a mayfly but for those who aren't, here's a brief overview.
I’ll call this Mayflies 101.The mayfly's life cycle is one of incomplete metamorphoses - a big word that means
he or she starts their life as an egg and then becomes a nymph that has several stages of growth called
instars. In other words the mayflies get larger and larger during the one to two years (usually one) that they
are nymphs. When they hatch, they turn into adult flies which anglers call duns.
In short, the life cycle of
a mayfly is an egg, a nymph and a dun.
During its entire life, which is usually a year but can be two
years depending on the species, the mayfly is a fly with wings only for a day or two, sometimes not even
that long. Caddisflies and Midges undergo complete metamorphoses which means they insect start as an
egg, then become a larva, then a pupa and finally an adult.

Types of Mayfly Nymphs:
There are basically four types of mayfly nymphs. The swimming nymphs that actually can swim, some like a
minnow, but others not so good. In Yellowstone, the
Baetis species and most other Blue-winged Olives are
swimmers. The swimmers are available for trout to eat most of the time.

Then there's the burrowing nymph that lives most of its life in burrows in the bottom of the stream's soft soil
or fine gravel. Most of these are the big drakes. These are only available to trout some of the time, mainly
when they come out of their holes to eat or hatch.  There are a few burrowing mayfly nymphs in the
streams of Yellowstone.

The clinger nymphs can attach themselves to the rocks by suction and live most of their life under rocks in
fast water. They are only available to trout at certain times - such as just before they hatch and when they
expose themselves to eat. There are a lot of clinger nymphs in the streams of Yellowstone.

And finally, there are the crawler nymphs. For the most part, these are moderate water nymphs but their
habitat can vary quite a bit. Pale Morning Duns are examples of crawler nymphs. They are available to
trout much of the time. There's a lot of crawler nymphs in the streams of Yellowstone.

A swimmer mayfly nymph looks and behaves as much like a clinger nymph as a deer looks and behaves
like an antelope. A crawler nymph looks and behaves as much like a burrower nymph as a moose looks
and behaves like a buffalo. Trout can see the mayfly nymphs much better than the duns. Having a fly that
looks like and act like the most plentiful and available nymphs for the trout to eat at the particular time you
are fishing gives you the highest odds for success.
To do this, you need to know which type of nymph
you are trying to imitate.
Otherwise, your relying strictly on luck.

Copyright 2012 James Marsh