If you fish in Big Sky Country, or anywhere else trout live, you undoubtedly know about Drakes.

If you don’t, you should. They are the kings of all mayflies. Their size (#10-12) commands respect, and demands attention from fish and fishermen alike.

The most famous of the Drakes is the Green Drake, Drunella grandis. Brown Drakes, Ephemera Simulans, are a close second. And, the Gray Drake, Siphlonurus occidentalis, shrouded in mystery and misconception, ranks third.

Gray Drakes are found in several of Big Sky Country’s renowned fisheries, as well as a few of its sleepers.

The most notable Gray Drake activity in Big Sky Country is on the Lower Henry’s Fork below Ashton, ID. In Yellowstone Park, Gray Drakes can be seen in popular waters like Slough Creek, and the Yellowstone River above the falls. Less popular spots to encounter Gray Drakes in the Park include the Madison, Gibbon, and Lewis Rivers.

Gray Drakes may be the least celebrated of these esteemed mayflies, but they are hugely important, and provide outstanding opportunities for fly fishers in Big Sky Country.

Here are Four Geeky Bug Facts about Gray Drakes that will help you catch more fish.

1.   The Duns Have an Identity Crisis

It’s hard being the lesser-known, underappreciated member of the Drake family. So, it’s understandable that Gray Drake duns would behave like something they are not – stoneflies.

Most mayflies live as nymphs in the bottom of lakes, rivers, and streams until it is time to complete their life cycle, at which point they swim to the surface and emerge as duns creating the one event that all fly fishers hold near and dear to their hearts – the hatch.

For many anglers, a hatch is the pinnacle of fly fishing. It’s the one time that both bugs and fish come to the water’s surface and allow us to interact with them and watch as the excitement unfolds.

Gray Drakes, however, rob us of this opportunity, choosing instead to act like stoneflies and crawl out of the river to emerge on stream side rocks and vegetation.

This is one of the main reasons that Gray Drakes don’t receive the accolades of Green and Brown Drakes. In fact, many experienced fly fishers have never seen a Gray Drake Dun. Although, a close examination of riparian rocks, grass, and willows will sometimes reveal these elusive duns waiting to molt into spinners.

Gray Drake duns are impressive in size and stature (#10-12). Their dark, slate gray wings slope over an olive gray body with distinct brown markings.

While Gray Drakes don’t necessarily present a chance to “Match the Hatch” they can produce savage eats along the banks on windy days. On rivers like the Henry’s Fork, where there is a sturdy population of Gray Drakes, resident bank-dwelling brown trout are accustomed to seeing these stately duns with the same frequency as terrestrials like hoppers and beetles when the wind blows.

2.   The Spinners Suffer from Goldilocks Syndrome

If you have fished with Gray Drakes before, it was most likely with the spinner imitation. As cagey as the duns may be, the spinners are equally prolific. But, like Goldilocks, they want things to be just right.

Dense mating flights and corresponding spinner falls of Gray Drakes can occur anytime from mid-morning to evening. Research suggests that mating flights and egg laying activity seem to peak between 60 and 70 degrees Fahrenheit. And, despite their large physique, Gray Drake spinners cannot cope with much more than moderate wind.

In Big Sky Country, the Gray Drake spinner Goldilocks scenario generally occurs on relatively calm days from mid to late morning after temperatures have had a chance to warm, and again in the evenings when the heat of the day subsides.

Like Goldilocks, Gray Drake Spinners want everything to be just right. Some days have a perfect combination of variables with little wind and moderate temps lasting throughout the day. These are the rare days that produce epic spinner falls with seemingly millions of insects mating and falling spent on the water. Other days are too cool or too windy, and the spinners never take flight, choosing instead to seek shelter in the riparian vegetation and wait for more suitable conditions. Some days the spinners take flight and tempt us as they hover high over the water only to vanish as soon as the wind picks up.

On most of the waters in Big Sky Country where Gray Drake spinners are found they will be a solid size 12. You will know you have found one if it has two tails, clear glassy wings with no mottling, and a rusty brown body with distinct horseshoe markings on the bottom of the abdomen.

3.   The Nymphs Perform Daily Flash Mobs

Ok, not really, but sort of…

Of all the geeky bug facts associated with fly fishing, few are more fascinating than the behavior of Benthic Drift.

This is a daily phenomenon where at the same moment all of the individual nymphs in a given area will release from the stream substrate and drift with the current.

It’s the aquatic macroinvertebrate equivalent of a flash mob minus the singing, dancing, and viral YouTube stardom.

Decades of research has been aimed at explaining Benthic Drift, but one widely accepted theory is that drift is a mechanism for insect populations to colonize new habitat after carrying capacity has been reached.

Like bison migrating to a new section of grasslands after grazing the first one, nymphs drift downstream in search of greener pastures. When adults emerge, molt into spinners, and form mating flights they move back upstream to deposit their eggs and close the cycle.

Gray Drake nymphs migrate in impressive numbers toward the stream banks in preparation for emerging, and they also perform daily benthic drift flash mobs. These strong swimming nymphs with slender bodies concentrate like schools of baitfish drifting with the current, and trout love to intercept them along the way.

Benthic drifts predominantly occur in the mornings and evenings, which, coincidentally, is the same time as Gray Drake spinner falls.

Few fly fishers would pass up the chance to fish a size 12 dry fly to rising trout, and opt instead to fish a dead drifted or stripped nymph pattern subsurface.

But, as we know, Gray Drake spinners have a bad case of Goldilocks Syndrome and need conditions to be just right. Not every morning or evening will be perfect for spinners.

So, at these less than ideal times, when spinners aren’t falling and fish aren’t rising, nymph imitations fished with a dead drift, or a short darting stripped retrieve can be productive.

4.   They Live in Lakes, Too

While extremely uncommon, there are some lakes in Big Sky Country which harbor populations of Siphlonurus mayflies.  As such, the savvy stillwater angler who likes to explore new water should probably be prepared with at least a couple of Gray Drake imitations in their boxes.  The first three facts about Gray Drakes apply in the stillwater environment, too.  Since they migrate to, and emerge from shore, expect concentrations of emerging nymphs (and feeding trout) in the shallows near shore, and don’t be too concerned about dun imitations.  Fish your nymph (whose colors vary greatly depending on the substrate and vegetation) with a retrieve that imitates their adroit swimming ability, with some occasional pauses for good measure.

Spinners will provide the best dry fly opportunities.  Look for the big spinners on the water, near shore, primarily on calm mornings.  Because they are such a shoreline dependent insect, this hatch is often accessible to stillwater anglers who are searching on foot.  These are BIG BUGS, so there is usually no mistaking them for other stillwater mayflies, like Callibaetis.  In our experience, spinners often sit on the water with upright wings, and the fish don’t seem that fussy about the fly pattern as long as the size is right, and the color is pretty close.

Now get out in Big Sky Country and find some Gray Drakes

Gray Drakes can be seen from June through September in parts of Big Sky Country.

Now that you know a little more about the inglorious Gray Drake you’ll be able to anticipate and plan for those epic spinner falls, and have some tricks up your sleeve for when conditions are ideal, and also when they aren’t just right.