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November Bug of the Month: The Baetis

With the grey skies of fall, drizzly conditions and the first snows, the conditions are perfect for baetis and Blue Wing Olive action. If you Google “hatch chart,” you’ll see that Blue Wing Olive / Baetis stretch across the page from March through November. So, yes, the prolific baetis returns as our Bug of the Month for November.

Director of Services, Jon Easdon, says that BWOs serve as sort of the “bookends of the fly fishing season. They emerge throughout the year, but we’ll get a great hatch in March and another one, but with smaller bugs, in the Fall.”

With such diversity within the species, its wide range, and the fact they are petty hardy insects, it’s always good to carry a few patterns in your fly box 365 days of the year.

Lifecycle of the Baetis

A few things to keep in mind: With such a large number of species and variation of size, color, and profile, matching a baetis hatch can be a bit overwhelming. It’s not uncommon for a handful of different baetis species to be emerging simultaneously. For this reason, it’s important to consider the lifecycle as we talk about fishing the baetis

Another distinguishing factor is the relatively fast lifecycle of the baetis. From egg to larva (nymph stage), to emerger, to adult dun, the lifecycle may be only a few months compared to other aquatic insects. That’s why we can have a heavy hatch in late winter and early spring and another in the autumn. Hatches can happen throughout the year and are heavily dependent on water temperature. 

Fishing the Baetis


In the fall, size is going to be a key factor. Go smaller and sleeker than you would in the spring and summer. Size 22 and 24 patterns need to be in your fly box now.

As the baetis transforms from egg to nymph, it seeks out shelter under rocks for protection.  When the nymph begins its migration, its goal is to reach the surface. Sometimes nymphs will move toward the bank so their swimming journey to the surface is shorter. 

Brown Pheasant Tails and Hare’s Ears are effective patterns at this stage. And don’t forget the RS2.


As they move to the surface, they begin to shuck their bodies. In this emerger stage, they can become even more vulnerable. 

Fish will follow this lifecycle, moving up in the feeding column as the baetis change form during the hatch cycle. Adjusting for depth is important because fish may be feeding on larva toward the bottom and emergers up to the surface.

If you aren’t seeing many rising fish, try fishing with a nymph as your first fly followed by an emerger.  Barr’s Emerger is a go-to, for sure.

Sometimes the fish’s rise can be confused for fish feeding on the surface. In fact, the fish may be eating emergers beneath the surface.  As the emerger is shucking its body to become a dun, they often times have trouble breaking through the tension on the water’s surface. Watch for fins and tails in the rise. Drift an emerger behind a dry fly can be deadly when the emerger is in that two or three inches just beneath the surface.

Similarly, color matters. Grey and olive may work for awhile early in the day but it may be productive to switch to brown and rust colors as the day progresses and temps increase.


Of course, the adult baetis in the dun stage, the Blue-Winged Olive, is very identifiable. Once the emerger breaks through the surface, they sit on the water until their wings dry. Their wings look like sails on a boat.

One of the angler’s best friends is an overcast sky. Because of he cloud cover, the adult dry fly, the dun, has to stay on the river’s surface a little bit longer for their wings to dry. Colorado overcast days can make for incredible dry fly fishing.

The mayfly has a second adult stage. After they dry their wings and fly, they usually make their way to foliage along the banks. At this point, they evolve to their sexually mature stage. (We’ll respect their privacy here.) Then, the female makes her way to the river to lay her eggs. This begins the spinner stage.

With this transition, you’ll begin to see noses as trout sip the adults off of the surface. Switch it up to light grey or tan patterns. Presentation is going to matter here, too. Anglers may want to breakout a new 9’ leader to get a drag-free drift on the smaller adult patterns.

The BWO is in its dying stage. The bodies are more elongated and in this dying stage, they change colors, often to a more rust color. 

Tying the Pattern

Check out Hopper Juan Ramirez’s Hi-Def Baetis pattern:

Neil Luehring ties up his BWO adult. Great pattern for our tailwaters!

Have you checked out our online store to purchase fly assortments for our local fisheries?  And watch our fishing reports so you know what is hatching, where, and info on up-to-date conditions.

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