The Western Green Drake is a good hatch for fly fishing in Missoula, MT, but not the easiest to predict. It doesn’t come off as heavily as other hatches in the area, but can be strong in certain places at certain times. As with many early season mayflies, the hatch is triggered by water temps, and due to factors like runoff, rain and varying weather, the Green Drake isn’t a hatch you can set your watch to. But they’re a sizable bug, and when they start hatching in early to mid-June, they’re big enough to pull fish off of the Salmon Flies and Golden Stone! So it pays to have some Western Green Drake imitations in your box, especially when the weather is cloudy.
There are two main species of Western Green Drakes, Drunella Grandis and Drunella Doddsi. D. Grandis max out at 16mm while D. Doddsi maxes out at about 13mm. We have both on our waters, imitated by the same pattern, in size 10 or 12, and applies to nymphs and dries equally. The nymphs don’t hatch at the surface, they hatch about a foot below the surface, and then float to the top to use their wings to break through the surface film. While this emergent phase may be critical on rivers like the Henry’s Fork, where the Green Drake is a blanket hatch, in Missoula the sparser nature of the hatch means fish keying on the Drakes are a much less fussy.
Using the wings to break through the surface film causes additional stress to these insects. When these insects do emerge, their wings are pretty beat up, and many of the adults don’t actually make it to the stage where they can fly off the water. A Green Drake Cripple, such as a Sir Francis or a Quigley Cripple are excellent imitations of the drakes that don’t make it.
The Western Green Drake uses a liquid to fill the veinations through its wings. That process takes time. And depending on air temperatures, the Green Drake wings can take a long time to dry. On colder days, the bugs may float for over a minute before their wings are full and dry and capable of flying. The dry fly is a subject of some debate amongst tyers and fishermen. In Missoula, Green Drakes hatch when the rivers are running pretty big. On the Blackfoot River and Rock Creek, you may want to use a Green Drake pattern with strong flotation, like a Hairwing Green Drake. But when Green Drakes hatch on the Clark Fork River or Bitterroot River, which are much lower gradients, use a more imitative pattern like a Carnage Green Drake or an Tilt Wing Green Drake. That’s not to say that the flies listed are river specific, we’re simply saying that a big, bouncing river will sometimes need a higher floating fly than a calmer river might require.
The Green Drake isn’t always the friendliest of hatches for the wading angler. The rivers are big when it starts coming off, and sometimes a wading angler simply can’t get to where the insects are hatching. As with most mayflies, if you can set yourself up downstream of a good, strong riffle, these crawler nymphs will hatch down into the slower water often found below riffles. And of course, in all high water, the fish are hugging the banks, looking for the softer water. With an insect that may float for a minute on the surface, it may not be critical to be near where they’re hatching, only to be near where the fish can find
soft enough water to rise!
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