.......................  ....................  ...Fly Fishing Yellowstone National Park
4/28/12

New KISS Bug Series - Part 4
Bugs 101

The Mayfly Hatch, Egg Laying and Death:
Near the end of the first year or second and even the third year in a very few cases, the mayfly nymphs
hatch. Technically, animals which includes insects, hatch from eggs. When a mayfly nymph changes into a
dun, anglers call the process a hatch but emerge is a better description. In other words, the mayfly nymphs
turn into flies. They do this as follows:

1. Swimming to the surface and shedding their nymphal shucks.

2. Crawling to the bank or up rocks or plants to emerge.

3. In some cases, emerging on the bottom and swimming to the surface as a fly.

You need to know which way this activity occurs, when it occurs, and where in the streams it occurs for all
of the mayfly species you may encounter.

Most of them swim or float to the surface (aided by gas bubbles) and hatch into a fly anglers call the dun.
During this time they can easily be eaten by trout. They have no defense. This is when we fish an emerger
fly pattern, or a fly that represents the nymph changing into a fly with wings.

If the nymph crawls out of the water to emerge, we don’t need to imitate the dun. The dun will never touch
the water. For example, Gray Drakes hatch in this manner.

When the mayflies hatch, they fly off to the trees, grass or bushes for a short time. They stay there for a
few hours but depending on the particular mayfly species and the environmental conditions, it can be up to
two or three days. During this time, almost all duns change into what anglers call a spinner. They actually
shed their thin shucks, their tails get longer, and their wings get clearer. In layman terms, the mayflies
become sexually mature.

After they become a spinner, the males will usually congregate out over the water. They usually dance up
and down, supposedly to attract the females, who join them shortly afterwards. Then they mate and the
males quickly drop dead - similarly to the way a lot of us older men will probably die.

In most cases, or with most mayfly species, the females fly back to the trees, their eggs develop or ripen, if I
get by with calling it such. After a few minutes or hours, again depending on the species and the weather,
they fly back out over the water and deposit their eggs.

1. Some mayflies drop them from the air.

2. Some dip to the water and drop them.

3. Some dive to the bottom and paste them to rocks and plants.

You need to know which way each species of mayflies do this or you simply don't know what your doing
when you attempt to imitate the egg laying process.

After depositing their eggs, the females die and fall to the water, or if they dive to deposit their eggs, they
rise back to the surface and float off in the current. If they drop their eggs from the air you do not need to
imitate the female spinners at all as an egg layer. You may imitate them after they fall dead in what we call
a spent position with the wings flat, but there's no need to imitate them dipping to the water or diving under
the water. If the mayfly dives to deposit her eggs, you need to be fishing a wet fly to imitate the activity.

Copyright 2012 James Marsh