Basics of Fly Fishing - Trout Food Series - Mayflies - Part 5
Before I start, there is one thing you should keep in mind if you are not that familiar
with insect classifications. A
family of insects is a large group of species that are
similar. The insects are then classified into smaller groups with certain similarities
called the
genus. There could be from one to several different genera within the
same family. Within a genus, there could be from one to several
species. So when
I say family, I am referring to a large group of similar mayflies. When I say genus, I
am referring to a smaller group of mayflies within a certain family. A species is one
that is uniquely different from others within any genus.

You could describe a mayfly in the Baetidae family as being a
Baetis (genus),
tricaudatus (species). Just remember a family is a big group of mayflies, a genus
breaks the family down into a smaller group of mayflies, and the species are the
individual members of the genus and family that are uniquely different from one
another. It doesn't mean they have to be a different color or size. They may even
look the same to the naked eye but they can also, look completely different. This is
the only way anyone can be certain they are referring to the same insect.

The Blue-winged Olive Mayflies:
The Blue-winged Olive isn't a common name for any one species of mayflies.
There are many species of them called Blue-winged Olives. As mentioned, I will use
the scientific names because I will have to for you to understand what I am referring
to. You do not need to know them at all. I just want you to see the different mayflies
that anglers and most all fly fishing books and magazines group into this one
category of mayflies.

There are over 15 species of mayflies found in the park that anglers call
blue-winged Olives.

Baetidae Family:
Baetis species:
Most often when anglers mention Blue-winged Olives, they are referring to Baetis
species (members of the Baetidae family, but even then, there are several different
species of them. Fortunately, they all look and behave very similarly. Just for the
record, there are four
Baetis species that are found in the Smokies. The problem is,
the name Blue-winged Olives doesn't just include the
Baetis species. Other mayflies
are called BWOs (I will shorten it to BWO from now on).
Acentrella Species:
There are two species of mayflies in this group that are called BWOs. These are
often called Tiny BWOs, Little BWOs and mostly
Small BWOs. They are very
similar to the
baetis species but inhibit slightly different types of water. .  

Ephemerellidae Family:
Drunella Species:
There are also five species of Drunella family species that are found in the park.
They aren't even in the Baetidae family. They are in the Ephemerellidae family.
There's a huge difference in these and the
Baetis mayflies, but they are called
.. These are more correctly called Eastern Blue-winged Olives, to help
distinguish them from the others but that name is not usually used to separately
identify them. The appearance of these mayflies is similar to the
Baetis. The same
flies will work for all of these mentioned so far. We will be discussing them
separately because they hatch at different times and they behave differently. They
are crawler nymphs whereas the
Baetis are swimming nymphs. You can use the
same flies, but you should use different tactics to imitate them.
Attenella Species:
There is one species of these mayflies. They are called Small Eastern
Blue-winged Olives
in most part of the East but just BWOs in the Smokies. They
can hatch heavy in isolated areas.

That is a total of
twelve different species of mayflies from two different families
that are called BWOs in the Great Smoky Mountain Park. These mostly hatch at
different times of the year. Sometimes, there could be one or more species
hatching at the same time.

Here is another catch to it. Some of these species hatch twice a year. These are
bi-brooded mayflies. The nymphs don't live but for a little less than six
months before they hatch. All the others live for almost a year before they hatch. In
other words, you could have as many as 16 or 18 completely different BWO
hatches that take place in the Smokies.

Hang on now:
Now so far, I haven't done anything but try to explain why BWOs is a catch all name
that includes a lot of different mayflies and a lot of different hatches in the Smokies.
These little mayflies do vary slightly in color in all stages of their life but not much. In
the fast water streams of the Great Smoky Mountains, one fly for each of the stages
of their life will work just fine. The problem is, at any one time you need to know the
size of the ones hatching. You also need to know which of the two families of
mayflies they are in because they behave differently.

Since they most all hatch at different times of the year, and since these times
overlap in many cases, it is almost impossible to pinpoint the times by species.
What I do is to separate them into groups. In general, you have a
spring hatch
and a
fall hatch of the Baetidae family members. The Ephemerellidae family
members, Eastern BWOs,
hatch in the summer and early fall, depending on the
species. In other words, there are roughly three separete times the BWOs hatch
during the year. That is what you need to focus on first. Secondly, you should focus
on the size of the one or more species that are hatching at any given time. Thirdly,
you need to know which family they belong to because later on in this series, I will
get into the difference in the way you should fish the hatch.

Please don't let all these different species and names, especially the Latin
names throw you off.
They are only important in understanding that there are a
lot of these little mayflies, they hatch at roughly three different times of the year and
there are some difference in the way you fish imitations of the two different families.
If you just comprehend that you are in good shape. The good part is that the
same flies will work for them all. Tomorrow we will get into fishing the first early
season hatches of them.

Just for the record, here are the 12 mayflies called BWOs in GSMNP.
Baetis brunneicolor
Baetis intercalaris  
Baetis pluto
Baetis tricaudatus  
Acentrella ampla
Acentrella turbida
Drunella cornuta
Drunella cornutella
Drunella lata
Drunella longicornis
Drunella tuberculata
Attenella attenuata

Copyright 2010 James Marsh