The BWO: October Bug of the Month

Wait. What? BWOs were the Bug of the Month in March. What’s going on here?

That’s right. With the overcast skies of fall, maybe drizzly conditions and the first snows threatening, the conditions are perfect for baetis and BWO action. So, yes, it is BWOctober and the fall baetis enjoys the spotlight as our Bug of the Month.

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 October.”

Jon Easdon, Director of Services

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 BWO 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. 

A 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 early autumn. Hatches can happen throughout the year and are heavily dependent on water temperature. 

Fishing the Fall 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 swim to the surface is shorter. 

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

The Emerger

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.

The Adult

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 Baetis/BWO

Neil Luehring has been a part of the Angler’s Covey crew for just about as long as anyone can remember. In addition to his contribution as a guide, part of his long history with the Shop includes teaching many of the fly-tying classes over the years. In this video, Neil takes us through the steps for tying his BWO adult pattern. We can barely keep them in the fly bins.

Check out the Orvis website for great videos, including this one for tying Barr’s Emerger.

Final thoughts

Fall fly fishing in our local area cannot be beat. We may have to put on an extra layer for those overcast days, maybe some drizzle, but the rewards are worth it. Head into the shop and talk with our expert team to make your BWOctober a great month!

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.