Do You Know the BWO?

by Robert “The Bug Guy” Younghanz

If you check any “hatch chart,” you’ll see the Blue Wing Olive stretch across the page from March through October. This prolific mayfly serves up a consistent diet for trout in Colorado and fills up a good portion of an angler’s fly box, too. Hang around any fly shop, and you’re likely to hear guides say, “BWOs were poppin,'” at some point in the conversation. What is it that makes this bug so interesting? We asked “The Bug Guy,” Robert Younghanz, about the science of the bug.

BWOs, or Blue Wing Olives, are in the mayfly family Baetidae. As an entomologist, guide and angler I find these “small minnow flies” to be one of the most fascinating groups of aquatic invertebrates. They are like a good friend who is always there for you, and there are some core biological reasons for this.

First off, Baetidae is not only the most prolific family of mayfly in Colorado with around 20 species, but the count expands to 140 species in North America and almost 1000 worldwide. It’s no wonder that BWOs are one of your best friends as a fly fisher and always on the menu for trout.

Depending on temperatures, BWOs can be seen emerging every month of the year, although March-October are prime. With such diversity in species, large dispersal range and the fact they are kind of rough and tumble as far as mayflies are concerned, it’s always good to bring a few imitations with you to river 365 days of the year.

Join Juan Ramirez and Neil Luehring in our virtual fly tying class focused on BWOs: Friday, April 10. 7:00 – 8:30 pm. Register here. Juan is excited about this online opportunity to share his tying techniques and style with you. “It’s about being precise and having a specific purpose at the vise which translates into having a specific purpose when fishing these flies.” Neil’s Blue-Winged Olive pattern is one of the most difficult to keep in the shop! He’ll be demonstrating some variations — both dark and light wings,and, if time allows, parachute versions. When it comes to BWOs, Neils says the biggest challenge is getting the proportions right. His Blue-Winged Olive pattern is featured in Pat Dorsey’s Colorado Guide Flies, so come and get some first-hand insight on tying this killer pattern.

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. The South Platte River drainage contains all 20 species of BWOs in and of itself! While sometimes precise selection doesn’t matter, there are times when choosing the right size and color right makes a huge difference on how productive your day is. The point here is to do some collecting, examine these awesome little guys in great detail, and then pick your pattern accordingly. Trust me, one size does not fit all.

Along with demonstrating the Jedi Master, Juan will focus on the Slim Shady & the Sniper Baetis. Follow Juan on Facebook at The Hopper Juan

If anything, next time you’re in our fly shop and you notice that we carry so many varieties of BWO patterns, you’ll understand why!