To most anglers in the Rockies spring means one thing -- Blue Winged Olives, sometimes called simply “BWO.”  These diminutive mayflies are the first indication that winter is releasing its grip on the mountains.  They also offer the first true chance for some dry fly fishing in most locations, which makes them highly thought of among fishermen everywhere.

    There are actually dozens of species of mayflies that fit under the heading “Blue Winged Olives,” most members of the genus Baetis.  So far as anglers are concerned, this really doesn't matter.  All of these species are represented by the same flies, with only slight variations in color and size between them.  All BWO nymphs fall into the “swimmer” category of mayflies and can be found in all different types of water, though moderately fast riffles and runs usually hold the largest populations.  Often, the most prolific dry fly fishing will be found in the tailouts of runs and the flats between riffles as the trout feed on freshly-emerged duns drying their wings in these slower sections of river.

     Trout feeding on Blue-Wings tend to rise subtly and rhythmically, so you should look closely for snouts and fins breaking the water surface.  I find that I'm most successful when I target individual fish, rather than “flock shooting” into a group of risers.  Observing and stalking individual fish will allow you to see what stage of the hatch the fish is keying on and where in the current he is feeding.  A little keen observation will also help you pick out the largest fish in the pool and target it.  I've seen many anglers throw their fly into a pod and get excited about hooking up with a fifteen-inch trout when a little patience and observation would have given them a chance at the eighteen-incher feeding in the scum line three inches away.  If possible, I like to position myself slightly upstream and across so I can make a fly-first downstream presentation to the trout.

   The following are some of my favorite BWO imitations for spring, followed with their recipes and some notes on the fly.  Give them a try next time you find you're on the water, I think you'll be very happy with the results.

"Mercury" BWO Nymph

• Hook: TMC 200R, #16-22
• Bead: clear glass
• Thread: olive-brown UTC 70
• Tail: olive pheasant tail
• Abdomen: thread
• Rib: 3/0 black monocord
• Wing Case: black antron
• Thorax: olive-brown dubbing
• Legs: black antron

   I've been fishing this variation of Pat Dorsey's famous "Mercury" series of flies for a couple years.  I wanted the fly to be darker than those Pat had originated, so I added a black thread rib and used darker thread for the abdomen.  It's a simple tie and a great pattern to use as the first fly in a double nymph rig.

Flashback Biot Nymph

• Hook: TMC 200R, #16-22
• Thread: olive Griffiths 14/0
• Tail: Hungarian partridge
• Abdomen: olive turkey biot tied in "rib" side up
• Wing Case: medium pearl Flashabou
• Thorax: medium gray dubbing
• Legs: Hungarian partridge

     I first saw this fly in Shane Stalcup's book Mayflies: Top to Bottom.  I decided to tie some up for an upcoming trip to the Eagle River.  They worked so well that I came home and immediately tied up a couple dozen more to ensure my box was never without them again!  I have since used this fly on streams all over the Rocky Mountains and it produces everywhere.  You can easily change the biot color in order to imitate other species of mayflies.

Iron Comparadun

• Hook: TMC 101, #16-22
• Thread: gray Griffiths 14/0
• Tail: 2 white Microfibbetts
• Body: superfine Adam's gray dubbing
• Wing: steel blue Widow's Web™ tied in "comparadun" style

     I started tying this fly long before my skills allowed me to tie a "real" Comparadun.  I had a lot of success with standard comparaduns, but had so much trouble (and got too frustrated) tying them.  Therefore I decided to substitute the deer hair wing for a synthetic fiber that was easier to work with.  I have found this pattern to work equally as well as the traditional Comparadun, so I continue to tie most of my own Comparaduns in this manner.  Though the body color on this pattern is slightly different than those of most Baetis, I have found that picky fish will -- for whatever reason -- often take a gray fly with the same profile as a BWO after refusing more precise imitations.  I always keep a couple of these in my box in case I run into that one stubborn fish that doesn't like anything else -- chances are he will eat this.

Miller's Silhouette Dun

• Hook: TMC 2487, #16-22
• Thread: gray Griffith 's 14/0
• Shuck: olive antron
• Abdomen: medium olive quill
• Wing: iron grey antron, tied “Wulff style”
• Thorax: medium dun hackle clipped flat underneath.

   This is my “go to” fly during a BWO hatch.  I designed it to sit low in the water yet still be easily visible thirty feet away on an overcast day. The antron shuck gives the fly a suggestive sparkle in the water and the clipped hackle leaves a realistic silhouette (hence the name) on the water.  Since quills tend to be fragile, add a drop of head cement or glue to the thread under the abdomen right before you wrap the quill forward.  This glues the quill to the underbody, so that even if it breaks it will not unravel.

Kyle's Beerhead Baetis™

Photo courtesy of Montana Fly Company

• Hook: MFC #7045 scud hook, #16-20
• Thread: tan 8/0
• Bead: rootbeer colored glass bead
• Tail: natural Hungarian partridge
• Abdomen: MFC Frog's Hair™ dubbing, callibaetis
• Rib: small copper wire
• Back/Wing case: pearl mylar Flashabou
• Thorax: same as abdomen

    This is another great BWO nymph that I have used with success all over the Rockies, especially on technical tailwaters such as the South Platte and Missouri.  I think one of the major reasons this fly is so effective is that it's so different from patterns these trout regularly see.  This fly is commercially available from Montana Fly Company, but it's an easy tie. The rootbeer beads might be a little tricky to track down, but I've been able to get them at Hobby Lobby on a regular basis.

Trina's Bubbleback Emerger™

Photo courtesy of Montana Fly Company

• Hook: MFC #7045 Scud Hook, #14-18
• Thread: olve 8/0
• Bead: gold
• Tail: pheasant tail
• Rib #1: copper wire
• Rib #2: black Flashabou Accent or black Krystal Flash
• Abdomen: pheasant tail
• Wingcase #1: black Flashabou Accent or Krystal Flash
• Wingcase #2: pheasant tail
• Thorax: Wing-N-Flash, peacock

     This fly was originated by my friend Adam Trina, founder of Montana Fly Company and former Missoula, MT-based guide.  The black “bubbleback” wonderfully imitates the splitting wing case of an emerging insect and the fish definitely take notice.  I usually fish this fly under an indicator but will also fish it behind a dry on a greased line when the fish are looking up. You can substitute a tungsten bead to get the fly down more quickly if you are nymphing.  Trina's Bubbleback Emerger™ requires intermediate tying skills and a little practice to master, but once mastered it's easy to tie several at one sitting.  As a substitute for the thorax, try using peacock-black Ice Dub as it's much easier to find than the Wing-N-Flash material but produces about the same effect.