The Blue-winged Olive:
Many different species of mayflies are rightly called "Blue-Winged Olives"; however, there
is one thing for sure. The Beatis genus of the Baetidae family of mayflies, or those little
olive-gray colored mayflies, called Blue-Winged Olives, Little Olives, and a lot of other
names, are important tiny aquatic insects. They maybe the most important of all mayflies.
They are found in just about every trout stream in the United States. There are many
species, numbering in the dozens and in most streams they represent a large portion of
the trout's diet.
Baetis are found in moving water. They do not live in still water. Although 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. Freestone, spring creeks and
tail water streams also have blue winged olives.
The thing that makes them important in the eyes of most anglers 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. In many areas of both the Eastern and Western states, they
hatch off and on over a period of several months, beginning in the early spring or late
winter and continuing off and on until the fall hatches occur.
At times it is even possible to have two or even more hatches of different species of little
olives occurring at the same time on the same stream. The spinner stage of one species
may be present along with the dun of another. It is not real important to know each of 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 greatly,
depending upon the species.
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 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.
We have organized the "Baetidae" family to include nine major species. There are many
more species in the Baetidae family, but these include the most common ones found on
trout streams. Chances are very good that any of the rare of less common species you
may possibly encounter, will be very similar to the mayflies included.
The tricaudatus species is found in the West, East and Mid-West. The bicaudatus
species is found only in the West. The flavistriga is found in the mid-west and hatches
over a very long period of time.
The punctiventris species is found in the West and Mid-Western States. The dubium
species is found in the East and the Mid-West and the futile is a Western species.
The baetis brunneicolor can hatch up to five months of the year nationwide. The
flavistriga is only found in the Midwestern states.
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