What is a Blue-winged Olive?
Copyright 2014 James Marsh
species from more than one family of mayflies. The later would be correct. Blue-winged Olive is a "catch all" name of many different
species of mayflies that usually have various shades of light, blue wings and various shades of olive bodies. The majority of these
mayflies come from the Baxxxx family. Most of them probably come from the baetis genus of the Baetidae family of mayflies.
The good thing about common names is they are names of aquatic insects that are commonly used, and the bad thing about them
is they are names of aquatic insects that are commonly used. The name can both simplify the identification of the insect and
confuse the identification of the insect, depending on the section of the country it is being used, as well as the particular angler
using the name.
Common names of aquatic insects do not really identify specific species of aquatic insects. They don't even identify specific
genera, or families of aquatic insects. They are just names that many, and in some cases probably most, anglers use to identify
insects. The names are also used to identify trout flies. They are used both ways - to identify insects and to identify flies that
imitate certain insects. When an angler uses the term or name "Blue-winged Olive", you don't necessarily know if he or she is
referring to an insect, or a fly that imitates an insect. The name is usually extended to identify the stage of life of the mayfly. For
example, there is a "blue-winged olive" dun, "blue-winged olive" emerging dun or emerger, "blue-winged olive" nymph, and
"blue-winged olive" spinner. Each of these names can be used for the actual insect and/or for the fly that imitates the insect.
Most of the time, depending on the general area or part of the country you may be fishing, the name Blue-winged Olive is referring
to a baetis species of the Baetidae family of mayflies. There are many different baetis species. The most common are the baetis
brunneicolor, B. tricaudatus, B. flavistriga, B. bicaudatus, B. cinctutus, and B. intercalaris. There are other less common baetis
species. There is also the Diphetor, Labiobaetis, Acerpenna, and other genera that have species called Blue-winged Olives. The
Diphetor hageni and Diphetor devinctus, for example. The Labiobaetis propinquu and Acerpenna pygmae are two more examples.
All of the above insects are "swimming" nymph mayflies. Therefore, most Blue-winged Olives are the names of mayflies that have
To make matters a little more confusing, the common name "Blue-winged Olive" can also refer to mayflies that are in the
Ephemerelliidae family of crawler mayflies. These Blue-winged Olives are in the Drunella genus, which happens to be the same
genus as the Western Green Drakes and Flavs, or Small Western Green Drakes. If you look closely at a Western Green Drake or
Flav, you will notice that although much larger in size, they too have olive bodies and medium-gray wings. It wouldn't be a far
stretch to call them Big or Giant Blue-winged Olives but no one does. The mayflies of the Drunella genus usually have the word
"Eastern" added to the blue-winged olive name, or an "Eastern Blue-winged Olive". By the way, there is also the "Small Eastern
Blue-winged Olives". Small Eastern Blue-winged Olives are attenuata species of the Attenella genus.
Often, the word "little" is added to the blue-winged olive name. Again, there is no exact definition of the name, but this usually
means the name is referring to the margarita species of the Attenella genus of the Ephemerellidae family. These little mayflies are
found in the eastern, mid-western and western parts of the country.
The word "small" is sometimes added to the name. A "Small Blue-winged Olive" is usually used to identify the simplex and lita
species of the Timpanoga genus of the Ephemerellidae family. These are mostly found in the eastern and mid-western sections of
Now that you know what anglers usually call "small blue-winged olives" and "little blue-winged olives", keep in mind they also call
many other little or small (referring to the size) blue-winged olives the same thing adding even more confusion.
You should now realize the name "Blue-winged Olive" refers to many different species of mayflies, some of which are crawler
nympls and some of which are swimming nymphs. About the only thing in common, is the bodies are usually some shade of olive
and the wings some shade of light blue. Notice I wrote usually. I did that because many species of baetis, the most common genera
of BWO's, don't have olive bodies or blue tinted wings. They are usually fairly close but the bodies can be shades of light brown,
usually an olive brown and the wings of the duns can vary from light blue to gray.
By now many of you are probably beginning to wonder exactly what difference any of the details of this makes. In general, it
doesn't. At Perfect Fly, we don't make specific imitations of these various genera or species. We just have imitations of
Blue-winged Olive mayfly nymph, two types of emergers, duns and spinners. We tie them in four sizes from hook size 20 up to size
14. This covers most any of the above species. So, knowing the details about which species they imitate isn't that important in
terms of fly choice but it is important to know a few things about the difference in their behavior; different times, places and ways in
which they emerge; and different times, places and ways they die as spinners. If you know which of the species, or at least which
genera you are imitating, it helps you know how, when and where you should go about imitating the insects.
By how, I mean the best type of presentation. By where, I mean the type of water they live in or where they exist in a given stream.
By when, I mean the time of day and time of the season they live as nymphs, emerge into duns and die as spinners. For example,
some emerge on the bottom and/or mid stream and some on the surface. Some females dive and deposit their eggs on the
bottom, some drop them from the air and some lite on the water and deposit them.
The more you know about the particular species, or group of similar species you are dealing with, the better job you can do of
imitating their behavior. This greatly increases your odds of success.
March 2014 Issue
t doesn't matter where you go to fly fish for trout, you are likely to hear the name "Blue-winged Olive". Many anglers think it is
the name of a specific species of mayfly. Others would tell you it is the name of a family of mayflies. Some would tell you it is
the name of several different species of mayflies. A few anglerrs would probably tell you it is the name of several different
Blue-winged Olive Spinner
upside down under a leaf
Little Blue-winged Olive Dun on my forefinger
Blue-winged Olive Spinner