Baetis or BWO or ??
Baetis, let the confusion begin. Pronounced (beet-us) this little mayfly produces confusion among any fly fisher, intent on being precise in their identification of the ongoing hatch. To further complicate things the Baetis is really a family of insects, and what fly fishers call the Blue Wing Olive is actually a sub-species, yet is generally used to identify anything smaller than size 16, with a olive body.
For various reasons, I am here to say there is nothing wrong with that. For one thing if you are not an entomologist doing a thesis, all you really need to know is the approximate size and the approximate color, after that you can search your box for the closest thing. One thing in the angler’s advantage here is the size of the fly, Baetis are notoriously small, so not only are they hard for us to see, they are hard for the fish to see. Not that the fish have can’t see them, but the smaller the insect the less exact the pattern has to be. Small patterns have fewer things to trigger the ‘fake alarm’ in fish. Also Baetis hatches can reach blizzard proportions, the more frenzied the fish are, the more likely they are going to hit your imitation.
To further complicate exact identification, Baetis sub-species can have as many as five hatches per year. Each one can look slightly different to the careful observer. Depending on the time of year, or even the time of day, the diet of the nymph, the hatch can take on varying hues. I have had times when the hatch to my eyes was olive, yet the Adams was what the trout preferred. Trout don’t see what we see, and despite several authors claiming they know what a fish sees, I have my doubts.
Although by far Blue Wing Olive, is the most common name fly fishers use, the term is used to identify any number of sub-species. Other terms include Blue Dun, Little Olive, Tiny Olives, Little Slate Winged Olive, etc. Again the scientific identification is not as important, as is the imitation.
So what does the fly fisher need to know about the Baetis? Well here we go:
- They can hatch anytime of year the water is above 40 degrees, Fahrenheit. They prefer cloudy days. Hatches tend to occur mid-morning to mid-afternoon.
- They are small size down to size 24. Winter hatches tend to be smaller than summer.
- The nymphs are excellent swimmers, the emergers are not, and they tend to rise on bubbles, or hang in the surface film.
- While colors are predominantly olive, they can be brownish, or grayish. Wings are usually various shades of gray, with slight blue tones.
- Females actually lay eggs underwater, and are often times then swept away by the current, a wet fly imitation here works wonders.
There are probably more imitations for this genus of insect than all others. And there are oftentimes more than just the Baetis occurring at any given time, especially in spring and summer. So be prepared, despite their size sometimes fish can be annoyingly selective. I have found more often though they are selective about the stage of life they are feeding on then the exact color. For whatever reason fish tend to slurp the emergers relentlessly, and then they are calmer going after the duns. This is where patience and skill takeover. Be still as possible, present the fly drag free and very delicately, a parachute pattern helps here. Timing spinner falls can be difficult as the sub-species and time of year play a big part.