Blue-winged Olives
.............................Fly Fishing Yellowstone National Park

Although we have posted quite a bit of information on this site pertaining to hatches
and insects, we have very little information on how to go about fishing the hatches and
imitating the insects. It is of little value to just tie on a fly that is suppose to imitate a
particular insect if you really don't know how, when and where to use it.
Knowing and
imitating the behavior of an insect is far more important than having a good
imitation of it.
You have heard over and over that presentation is more important than
the fly itself and that is exactly what I am referring too.
During the next few months, time permitting, we will be posting information about
the hatches that occur in the streams of Yellowstone National Park and how to go about
fishing them. I will try to do this in advance of the hatches occurring this coming season.
This will include the mayflies, caddisflies, stoneflies and other aquatic insects along with
the terrestrial insects and other food trout rely on in Yellowstone waters.
We will start with the most confusing common named category of all the mayflies,
the "Blue-winged Olives". It is confusing only in the sense that the common name
includes so many different mayflies that are called "Blue-winged Olives". None of this is
complicated. Making the hatches simple is my sole purpose in doing this and
why the title of it is "Hatches Made Easy".
We (along with most books written on this subject) list what anglers normally
term "Blue-winged Olives" found in the Western United States down into (3) three
different categories;"Blue-winged Olives", "Little Blue-winged Olives", and "Small Blue-
winged Olives". The Small Blue-winged Olives will be covered later.  

Blue-winged Olives:
The first one, "Blue-winged Olives", is one of the first hatches of the season you
may encounter. This common name category consist of the
Baetis species of the
Baetidae family of mayflies. The following species are the most common species found
in the park but I am certain other Baetidae species exist.
(Note: The species scientific names are provided only for information for those that are
interested. It is not necessary that you know these species by name.
Baetis tricaudatus  
Plauditus punctiventris
(old name Baetis punctiventris) Little Blue-winged Olives
Blue-winged Olive hatches are usually taking place from the time the season opens but
this is subject to change depending on the weather and stream conditions. We will not
go into all the variations of the hatch times. You can review this subject by clicking on
and reading our hatch charts. This hatch occurs in about every stream in the park.  
These are swimming nymphs. Although the small, fast water streams have
populations of them, they are normally found in the quieter sections of the water such
as eddies and calm pockets along the banks. All of the larger streams have them and
some, such as the Firehole and Madison have tremendous populations of them.
The thing that makes them important is that they hatch over a much longer
period of time than most of the other mayflies. They can have more than one
generation in a year.  They hatch off and on over a period of months and are underway
when the season starts. They continue off and on, depending on the stream, until the
fall hatches occur.
As we said, It is not important to know  the species by name, but it
is important to
recognize and match the different sizes of the blue-winged olives.
Although the
colors do not vary that much, the size varies, depending upon the
As a general rule, the very early hatches usually produce mayflies much smaller
than those that occur during the warmer months of the year. Normally, in the hot
summer months, the hatches slow down but then pick up again as cooler
weather approaches.
In the colder months of the year, they tend to hatch during the warmest times of
the day, usually around noon. During the warmer months, the hatches usually
start occurring earlier, from mid-morning until late afternoon.
As with many species of mayflies, the hatches
usually last longer and are more
concentrated on cloudy, overcast days than bright sunny days
. In fact, stormy,
rainy, snowy and inclement weather days are usually produce the largest hatches.
When they do hatch, the trout can become completely selective on them and may even
prefer them to larger insects that are available at the same time. This fact has fooled
many anglers.

Coming Up Next:
Blue-winged Olive Nymphs

Copyright 2008 James Marsh