Mayflies 101

Most of you probably familiar with the life of a mayfly, but for those who don’t,
here is a brief overview. The mayfly life cycle is one of incomplete metamorphous
- a big word that means he or she starts their life as an egg and then as a nymph
that has several stages of growth or instars they are called. In other words they
get larger and larger during the one to two years (usually one) that they are

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 even less.

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 4 types of mayfly nymphs. The swimming nymphs that
actually can swim, some like a minnow and others not so good. The
species and most other Blue-winged Olives are swimmers. The
Isonychia bicolor, or Slate Winged Drake is a swimmer is a strong swimmer. The
swimmers are available for trout to eat most of the time.

Then there is 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.  

The clinger nymphs can attach themselves to a rock and live most of their lives
under rocks in fast water. They are only available to trout at certain times -such
as just before the hatch.

And finally there are the crawlers. For the most part, these are moderate water
nymphs but their habitat can vary quite a bit. Sulfers and Hendricksons are
examples of crawler nymphs. They are available to trout much of the time.

A swimmer mayfly nymph looks and behaves as much like a clinger nymph as a
deer looks like an antelope. A crawler nymph looks and behaves as much like a
burrower nymph as a moose looks like a buffalo. You need to know which type of
nymph you are imitating. Otherwise, to be frank, when you are fishing a nymph
imitation, you simply do not know what you are doing - much less what it is you
are imitating.
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