Blue Winged Olives

Fall Blue Winged Olives Part 1

Fall is just around the corner here in the Rockies and for or fly fishermen, one of the first signs of autumn’s return is the emergence of our beloved blue winged olive mayflies. These tiny mayflies hatch during periods of cool weather and become increasingly important to anglers as summer fades away. Trout tend to be picky about their blue wings, and this causes some frustration for many beginner fly fishermen. A basic understanding of the blue winged olive hatch and a few tips on how to fish it should help to ease the pain and put some more fish in your net this fall.

Hatch Basics

Hang out in any fly shop or at any boat ramp for longer than about twenty minutes and you will hear someone say the word “Baetis”. Fly fishermen love to say “Baetis”. Any time a fish eats something green, you can be sure that the word “Baetis” is soon to follow. For some reason, we as anglers have really sunk our teeth into the word “Baetis” while totally ignoring all of the sciency sounding Latin names of every other insect that we fish with. Either way, for the remainder of this article, I am going to call them blue winged olives. It feels better.

Blue Winged Olive Identification

Blue winged olives are extremely adaptable. They can live in almost any type of river bed, but they especially like rivers and streams that have a lot of aquatic plant life. One of the most important things to understand about the blue winged olives is that they are swimmers. This means that with the help of a tiny bubble of gas inside their slowly transforming body, they can swim up to the surface in order to hatch. Because of their small size, many struggle to get on top of the surface in order to go on with their metamorphosis. Trout often break the surface as they chase these swimming and struggling emergers upward, which fools anglers into thinking that they are eating the duns, when in fact, they are keyed in on the emergers. This accounts for much of our blue winged olive frustration, but not all of it. Many times, they actually are eating the duns and we are just not using the one that most appropriately matches the one they are eating. There are a couple ways that I know of to fix this problem, and I will explain them in part two.


The next thing we need to remember when fishing during a blue winged olive hatch is that these mayflies are very weather dependent. If it is a hot, sunny day in the beginning of September, they will usually only show up early in the morning and late in the evening, and only for a short period of time. If it is a cold, cloudy day in November, they will stick to the warm, middle part of the day, and can hang around for hours. My favorite blue winged olive hatches occur on days like the latter.

Because they are so small, and because they hatch during periods of cold weather, blue winged olive nymphs can have a difficult time emerging and transforming into adulthood successfully. Many of them end up crippled and never get airborne. It is for this reason that you should always keep a good selection of stillborn blue winged olive patterns on hand during the spring and fall.


With this information, you should have a basic understanding of what makes this hatch unique, and have a few ideas of how to adapt your fishing techniques to meet the specific demands of the blue winged olive hatch. In Part 2 of this blog, I will lay out of my favorite patterns for each blue winged olive life stage and talk about how weather and water conditions can give you clues about which one to use and when. Keep in mind that our FreakNFish fall special happens right around the time that the blue winged olives really get going on the Upper Colorado River. As with any big hatch, the best way to see these beautiful bugs is from the front of a drift boat, and the best way to learn how to fish with them is from a professional Vail Valley Anglers float guide.

Andy “Otter” Smith, Guide and Content Writer