by bob meseroll
photo by michael gallacher

It’s October.

Many fishermen are now afield with their bird dogs.

The day dawns gray and gloomy. A light drizzle falls and there’s a nip in the air.

That means just one thing to me: baetis, the foul-weather fly fisherman’s best friend.

The baetis mayfly is commonly referred to as a blue-winged olive, although its wings are not actually blue and its body is only somewhat olive. It’s one of the first mayflies to hatch on our Western rivers in the spring and one of the last in the fall.

It’s one of the hardiest mayflies around. On some spring creeks where the water temperature does not vary a great deal, baetis can hatch during the winter months.
And for reasons known only to the baetis themselves and to the most astute entomologists, they just love to come out and play on a gray day.

“The temperature is down and clouds are always a good thing,” said Kingfisher Fly Shop co-owner Jim Cox, describing baetis weather. “That’s one of my favorite hatches on the Clark Fork.”

“Once the clouds come out they blanket the water,” seconded Taylor Scott, a guide who works at the Missoulian Angler Fly Shop.

And sometimes even the most astute entomologists can’t come up with a definitive answer for why baetis love the gloom.

“I think most of us would say that hatches of BWOs often come off really heavy in the worst of weather,” University of Montana entomologist Diana Six said, adding that her specialty is terrestrials, not aquatic insects. “We see them hatch when it’s cold or dreary, but it seems they really perk up when it gets choppy and rainy and generally angler unfriendly. Why?

Good question.

“I am an evolutionary biologist, among many other things, so I tend to think of these behaviors as having an advantage or they probably wouldn’t have evolved. But in this case I have to say I just don’t get it. I don’t think it gives them more time to dry (expand) their wings. In fact, the worse the weather is, the fewer actually seem to make it onto the surface and off the water and the more cripples you see on the surface (and the better the response by the fish). So that would argue against greater survival at that time – come up then and you drown and or get eaten.

“But, there must be some reason. The bugs are smarter than me this time (as is so often the case).”

I’ll offer two examples to buttress our arguments for the fly’s proclivity to hatch in foul weather.

The first was Oct. 10, 1989. My first day as the assistant sports editor at the Billings Gazette was the previous day. When I arrived for work, all my belongings still in cardboard boxes in my apartment, my boss told me to take the next two days off.

My boxes weren’t going anywhere, so I headed to Fort Smith to fish the Bighorn.

It was the perfect storm of conditions: No wind, a high but thick overcast, an occasional sprinkle, and temperatures cool enough that you wanted a sweatshirt. On top of that, maintenance was being performed on the Afterbay Dam, so the flow was reduced, making it possible to easily cross the river and also congregating the fish.

Predictably, the blue-winged olives started early and kept up all afternoon. The action was so furious, I stopped counting fish – all caught on various blue-winged olive patterns – and stopped fishing when my shoulders ached.

My second argument is probably even stronger. It was early October of 2009 and my buddy Dale was visiting from Samoa. Normally a great time for fall fishing, it was unseasonably cold and records were broken left and right.

But when you’ve come that far to fish, well, you’re going to fish.

Temperatures were in the 20s when we set out on the Bitterroot in the morning and didn’t warm much above freezing throughout the day. We even tried applying Pam cooking spray to the guides on our fly rods to keep them from freezing up.

Quite honestly, I had low expectations. But darned if the blue wings didn’t hatch. We didn’t catch great numbers of fish, but to have any dry-fly fishing in that weather seemed nearly miraculous to me. It was the blue-winged olives that made it happen.

The list of blue-winged olive patterns is as long as my 5-weight.

Cox has a favorite.

“We have this one that’s a parachute blue wing,” Cox said. “It’s an olive-bodied dub with a black fibbet tail and a black hackle around a white post. It’s evil, it’s a bad bug. I’ve been fishing that ... for 30 years.”

One thing that I’ve found to be true for any hatch is that it pays to have multiple patterns in your box. If you miss a strike while using a particular pattern – and you don’t prick the fish or otherwise alarm it – it’s best to show them another pattern.

“I think if you can deal with fishing cripples that small, that the cripples are a really good alternative,” said Cox, a sentiment that was backed by Scott. “Quigley cripples in gray are great bugs.”

My personal favorites are sparkle and compara duns. They’re easy to tie and don’t require hackle, which can be tough to come by these days.

But I’ve also reverted to some old-school patterns in recent years. The thorax pattern is durable and easy to see on the water, which is good for aging eyes. And the really old-school standard pattern with hackle-tip wings can be a killer on flat water.

Attractor patterns can also be effective. Cox suggests a No. 16 royal Wulff and Scott likes a size 18 parachute Adams.

“If I’m dropping something off a dry fly, a size 18 or 20 hare’s ear (nymph) or something small that imitates the nymphal stage of those guys is good,” Scott said. “Maybe a foot under your dry fly so it looks like it’s swimming up, getting ready to hatch.

“They give a lot of action when they’re coming up from the bottom of the water chamber to the top. A lot of them try to swim back down, but they have these gas pockets that bring them up. Lots of them try to fight the current, trying to swim back down to the bottom. I think they say 70 to 80 percent of them die because they’re too exhausted trying to swim away from the surface because they don’t want to go up there.”

Both Cox and Scott agree about where to look for the fish during a baetis hatch.

“The backwater eddies, and I don’t mean big eddies, the little pockets at that time of year are isolated from the current,” Cox said. “If I’m fishing from the bank I put in a cast with a longer leader and let the fly line line up right against the bank, throw a curve in it so your bug is just a little off the bank and let it sit there without a drift. The fish, that time of year, tend to cruise the banks and pull into these pockets. That works fairly well.

“The other thing is to walk out into the river and fish back into the banks. You get fish working beats at that time of year way more than you do for the rest of the year.”

Some of those little eddies will contain foam. The duns get trapped by the foam and make for easy pickings for the fish. The foam can make it difficult to see your fly, but it’ll be worth the trouble in the end.

There are other fall hatches that get a lot of attention on our rivers, like the mahogany duns and fall gray drakes. Those flies are larger, easier to fish and elicit vigorous strikes, but I find those hatches somewhat less reliable than the baetis.

The blue-winged olive is an old, dependable friend.

“It signals a time when the season is winding down, you can catch your breath and you don’t see a lot of people on the river because a lot of people turn to hunting,” Cox said. “You see the tamaracks changing and the water’s really calm and you see that slow sipping rise form, which is a happy thing.”

Bob Meseroll is an avid fly fisherman who is not conflicted by the urge to hunt. He can be reached at 523-5265 or at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .