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Madison River hatCHES

A Guide To Bugs On The Upper Madison

The Madison River belongs in a special group of rivers, known world wide for its tremendous fishery and stunning scenery. A prolific and productive base of entomological life supports the fishery of the Madison River. We've put together a chart of what we consider to be the Upper Madison’s most important hatches. This isn't an exhaustive list, as there are approximately 114 unique taxa of macroinvertebrates on the Upper Madison, but it  covers the most important groups. For example, there are at least 31 different taxa of Midges, 23 taxa of caddis, and 6 different taxa of Blue Winged Olives . All of which likely produce varying levels of hatches which elicit feeding trout. However, for our purposes as anglers, we're interested in those hatches that are relatively predictable both in timing and reliably producing selective trout.

For those interested in a more science heavy breakdown of macroinvertebrate assemblage surveys conducted on the Madison, check out this blog post. For a specific breakdown of all taxa found in surveys of the Upper Madison


To understand the hatches of the Madison River, it’s interesting to consider the difference between a tailwater fishery and a freestone fishery with regards to aquatic insect life. Tailwater fisheries are those controlled by upstream dams. Dams regulate flows and water temperatures. Freestone streams have no impediment restricting flows or water temperature.


The Madison River is a strange beast in that it technically is a tailwater, with both a natural dam (Earthquake Lake) and man made dam (Hebgen Lake) upstream, but the shallow and fast flowing nature of the Madison combined with the many contributing tributaries below the dams forces the Madison to lose many of its tailwater characteristics by the time it reaches Ennis. For this reason, I would consider the Madison a hybrid. And the macroinvertebrate surveys reflect this spatial heterogeneity. Assesmbleges of bugs at the base of Hebgen are quite different than the suite of available macroinvertebrates near Ennis, for example. For more on these variations, see the blog post on surveys.


While this hatch guide provides dates for each hatch, these should be considered generalized. On the one hand it would be pretty convenient to know that the Salmonfly hatch, for example, will always begin on June 25th and last through July 10th year after year without fail. But it’s also part of the mystique that is the Salmonfly hatch, among others. Every year various hatches are slightly different by day from the previous. Generally speaking, biologists tell us the one driving constant that has the biggest impact on timing of hatches is photoperiod length (the amount of daily daylight). Aquatic insects mature as nymphs, or enter pupation from the larval stage, timed to the annual light cycle. Emergence within that window will depend on a variety of environmental conditions such as water temperature, water levels, daily weather, altitude, etc. Everyone has his or her own algorithm or theory, but nothing beats the anticipation of checking the river every morning for your favorite hatch to start!


So let’s dig in to the biggest and most popular aquatic insect hatches on the Madison River relevant to trout fishing!



Stoneflies have been crawling around stream bottoms for over 250 million years. And with over 600 species, one could spend a lifetime describing them. However, the importance and relevance to the fly fisher is much simpler. Stoneflies need a lot of oxygen and live only in water with good amounts of flow. This is why the upper Madison is reliably one of the best stonefly rivers in the world. Eight different species of stoneflies are present on the Upper Madison (Skwalas, 2 species of Goldens, 2 species of Salmonflies, 2 species of Sallflies, and Winter Stones). The constant riffle creates abundant oxygen, which Stoneflies thrive in.


Stoneflies have an incomplete metamorphosis, meaning they start as nymphs and morph directly to adults, which closely resembles the nymph. Emergence is exclusively the result of crawling to the bank and onto vegetation or rocks, typically taking place at night. Adults mate streamside and only return to the water to deposit eggs, which is when trout key in on their flying adult stages. Because adults hatch for only a brief time during the early summer, trout diets with regard to Stoneflies mostly focus on the nymph stage, which are active year round in the cobble. This is why Stonefly nymphs are perhaps the most popular and effective fly pattern on the Madison River, and is most effective when presented lower in the water column tumbling near the cobble.


Below are the most important species to the Madison.

Skwala Stonefly

Size: 10-12

Dry Fly Emergence Time Frame: March-April


Skwala Stoneflies are the first of the larger stonefly species to make their emergence in the calendar year on the Madison. They're also the most dominant stonefly taxa, by a mile. Skwalas begin their migrations in late February, with emergence peaking in March and April, and tapering off by June. The key is before runoff. Once Skwalas emerge as adults, they rarely are seen near the water’s surface more than 10 feet out from the bank. Interestingly, adult males have short, non-functioning, almost decorative wings and are incapable of flight. The females are the only ones flying, and with a purpose at that: dispersing eggs on the water surface. Emergence is more active on cloudy days, as with most other aquatic insects. Because Skwalas don’t typically fly much, you need to pay attention a little closer to find them, compared with later emerging Stoneflies. But this is your first chance of the year to get a fish to slap a chubby on the surface, so it’s worth a shot!



Size: #2-12

Dry Fly Emergence Time Frame: June-July


The prime rib of trout diets on the Madison River. So much protein stuffed into such a fat, helpless Salmonfly nymph bouncing down the river, trout must get drunk on these things. Spending 2-5 years in the cobble as nymphs, they grow to enormous sizes. Similar to Golden Stoneflies, Salmonflies typically start migrating toward shore from May to June and emerging to the excitement of fly anglers all over the Madison Valley, the last week-ish of June as water temps remain in the 50 degree range overnight. Nymphs make their move to the willows to dry out under cover of darkness. Trout and anglers alike stalk them along riverbanks up and down the Madison River as the hatch progresses upstream every day as water temps warm.

Golden Stonefly

Size: #4-10

Dry Fly Emergence Time Frame: June-July


The Golden Stonefly is a staple bug on the Madison River. One needs to be on the watch for river temps reaching 50 degrees Fahrenheit. At this point, migrations of Golden Stones begin en masse on the Madison River. Typically, this will begin occurring in late June early July. With a 2-3 year life cycle, Golden Stonefly nymphs are in the water 24/7, 365 just like the Salmonfly. Another reason to always have an imitation stonefly nymph handy.

Yellow Sally (Other Common Names: Little Yellow Stonefly)

Size: #12-16

Dry Fly Emergence Time Frame: June-July


Yellow Sally Stoneflies, with their yellowish tint, begin migrating to riverbanks in the Madison anytime during a long period from April through August. Not very specific, right? However, their emergence is largely in the late afternoon to evening hours in June and July. A copper john under a small stimulator is a fantastic combo when fishing a Yellow Sally Stonefly hatch.



Caddisflies are said to be increasing in importance in Rocky Mountain streams and rivers, supplanting Mayflies as the top aquatic insect on trout menus. Caddisflies are simply a little more resistant to changing environmental conditions. For example, where Mayflies might be sensitive and unable to emerge in warmer and siltier water condition, Caddisflies have showed no limitations to these conditions. More particulate matter and plant growth in rivers leads to more Caddisflies. Caddisfly abundance has also been linked to fatter trout, and who doesn’t like that prospect?


Caddisflies, as opposed to Mayflies and Stoneflies, have a compete metamorphosis with three stages: Larva, Pupa, Adult. Caddisfly larva have no resemblance to their adult stage. Generally speaking, Caddis eggs exist for 1-3 weeks, remain as larva for 9-10 months, then to a pupa for 2-5 weeks, and 2 days-5 weeks as adults. Because the majority of their lifetime is spent as larva, this is the most important stage for trout consumption as well. Adult Caddisflies come in a wide variety of sizes and colors but they all have the same basic shape: long antennae, short bodies, no tails, and large tent shaped wings held over their backs and extending beyond their bodies.


Although there are nearly two dozen species of Caddisflies on the Upper Madison, we’ll touch on the most prevalent ones here:


Spotted Sedge (Common Names: Cinnamon Sedge)

Size: #10-16

Dry Fly Emergence Time Frame: June-September


Spotted Sedge are a tan colored Caddisfly and are fairly ubiquitous across the west and have been known to hatch on the Madison From April-September. However, I’ve seen higher concentrations of Spotted Sedge From June-August mostly in evening hours. This species is a near perfect match for a Hare’s Ear nymph and a smaller tan Elk Hair Caddis dry. This bug creates some of the best Caddis dry fly action of the year!


Brachycentrus (Common Names: Olive Caddis, Mother’s Day Caddis)

Size: #14-18

Dry Fly Emergence Time Frame: April-June


Fly anglers across Southwest Montana look forward each year to the Mother’s Day Caddis hatch, typically occurring in the first few weeks of May during the warmest hours of the day. In some years, runoff has already begun and makes fishing the hatch difficult, but sometimes we get lucky and runoff holds off until after the hatch. It’s not uncommon to drive along the river during the thickest part of the hatch and need windshield wipers to clear your view. Certainly a buff is needed on the river unless you want a steady diet of the bug yourself. One interesting behavioral trait of the Brachycentrus is they typically do not move much once on the water surface as adults, so be sure to try dead drifting your Elk Hair Caddis first.



Mayflies make up a large share of the dry fly assortment of imitation flies in the world today. They dominate in available fly patterns. And that’s by no accident. Mayflies are often thought of as the perfect fly rod insect. They require cold, clean, flowing water just as trout do. They also emerge in open water on rivers and lakes, making them abundant throughout the stream and available to wade and float anglers. Third, the survival behavioral tactic employed by mayflies is mass emergence. The more of them that hatch at a single time, the more that survive predation. And lastly, they generally hatch during the middle of the day, just when us anglers are out and about. There’s also something to be said about the appearance and beauty of a mayfly that isn’t on display among some of the other aquatic insects.


Mayflies provide classic fishing to rising trout from April through November on the Madison River. Below are some of the most appropriate for the Madison.


Blue Winged Olive

Size: #16-18

Dry Fly Emergence Time Frame: Mid March-May and September-October


BWOs are a staple on most western trout streams and the Madison River is no different. Within the Batidae family, there are 6 species of BWOs on the Upper Madison. The most dominant of those is Baetis tricaudatus. In some reaches of the Upper Madison this species outnumbers the other BWOs 100 to 1. It's nymphal form is very olive, about a size 18 on average. The peak of the BWO season on the Madison is in late March and April, sometimes spilling into May a good chunk. But it's not uncommon to see BWO hatches in every month of the year. Hatches will typically be in the afternoon hours, and cloudy calm days are a bonus condition. In fact, with a light rain or snow, hatches can last up to a few hours, but on sunny days less so.

March Brown

Size 12-14

Dry Fly Emergence Time Frame: March-May

Sometimes inconsistent, this mayfly is a bigger mayfly and elicits big time strikes when they occur. And despite the name, they're more commonly found mid April through May on the Upper Madison. These mayflies overlap both the BWOs and Caddis hatches, and you will often see them hatching at the same time on any given day. The March Browns are unique because while they are often comparatively sparse in numbers, the fish will get keyed in on them, oftentimes to the exclusion of eating other bugs. From annual surveys, we know this mayfly is far more important near Ennis than near Hebgen. Late May seems to be the best time to find hatches of this larger Mayfly on the Upper Madison.

Pale Morning Dun (PMD)

Size: #14-20

Dry Fly Emergence Time Frame: June-August


PMDs are an often-overlooked species of Mayfly on the Madison River. PMDs can provide some of the most prolific hatches of the season with some of the most aggressive strikes from rising trout. As the hatch progresses in duration for the season, look for bug sizes of PMDs to get progressively smaller in size. PMD hatches also provide for some great evening spinner falls. Swinging PMD imitations is an excellent strategy during the initial phases of a hatch.


Green Drake

Size: #10-12

Dry Fly Emergence Time Frame: July-July


Although the Madison River isn’t known for it’s Green Drake hatch, it does have one. I often see drakes out during the salmonfly hatch on the float section of the Upper Madison which probably lends to it going relatively unnoticed, and is largely concentrated in the section of river known as “between the lakes” (Hebgen and Quake Lake) and for a very short time frame. It’s a tough one to catch, but it sure is a hoot if you do. We’re talking about larger mayfly patterns and it doesn’t take many to get fish actively feeding.



Size: 16-20

Dry Fly Emergence Time Frame: July-August


Tricos are extremely important at the mouths of all the various river outlets into Ennis Lake. This is because Tricos thrive in slower currents of rivers with vegetation, and the Madison definitely begins to slow before entering Ennis Lake and one starts encountering heavy weed beds leading into the lake. Tricos can hatch anytime between June and October, but are heaviest July through August on the Madison at Ennis Lake. Here you’ll find trout sipping on male duns at dusk or female duns in the first few hours of the morning. The daily summertime Trico hatch is an excellent opportunity to target trout taking dries in a concentrated manner. Because Tricos are typically very small (#16-20), you’ll need 4X to 6X tippet to effectively fish this hatch.


Callibaetis (Common Names: Speckle Wing)

Size: #14-16

Dry Fly Time Frame: July-September


Callibaetis hatches are generally associated with shallow, weed-filled waters, which is why these mayflies can hatch in spectacular numbers on Ennis and Hebgen Lakes. Nymphs, emergers, duns and spinners are all keyed upon. Targeting these “gulper” trout with a size #14 Parachute Adams is addicting. To bolster your odds even more, place a small non weighted pheasant tail about 6-8" under your dry fly to imitate hatching nymphs. If a lazy day of targeting rising trout with dry flies sounds appealing to you, a day of fishing on Ennis Lake is a treat.



Midges are the champion dry fly for winter on the upper Madison. With over 31 different species of tricos on the Upper Madison, they're everywhere. Hatching from November through April primarily, peaking in February, this bug is reliably present. Especially so on cloudy days. A size 18 parachute adams, griffith's gnat, or any other size 18 mayfly patters will do the trick. Trout don't seem particularly picky about the pattern. Just a dead drift and size profile. Since they're so tiny, and you're usually fishing them on flat light days, I like a pattern like the one above, with a little color post to help me find it on the water. Keep casts relatively short and use your stalking skills to get closer. This will help you find your fly better. 


Sculpins are in virtually all cobble bottom streams in the west and are abundant in the Madison River. They are present year round. Their habitat is along the bottom of streams and along riverside banks where large cobble provides safety and shelter between darts in and out of protection. Sculpin life cycles last from one to three years. Swimming streamer imitations on the Madison is something to be tried by every fly angler.



Beetles, ants, and grasshoppers attract not only the open mouths of trout, but fly anglers all over the west to Montana’s waters for “hopper season.” When is hopper season on the Madison River? Beetles, ants, and grasshoppers mature in late summer and early fall. This is typically from mid July to late September when grasses are brown and dry. I haven’t experienced much selectivity among trout when it comes to terrestrials, but aside from hoppers, I’ve typically had more success with ant patterns than any other terrestrial for whatever that’s worth.




Leeches live in a wide variety of aquatic environments, but for trout in the Madison River system, they are most important in the stillwater setting such as Ennis and Quake Lakes. This is because their preferred habitats are more readily available in stillwater environments. Those are calm, weedy, and slightly warmer waters. They feed on decaying organic material such as dead vegetative and animal matter.


Leeches also have no specific emergence period. They are active year round. If a body of water is open to fishing, particularly lakes and ponds, you can bet leeches are active and a good choice for imitating.




For the fly angler, there are three types of crustaceans that should be important: scuds, sow bugs, and crayfish. All are protein rich and sought out by trout when available. Crustaceans have no aerial stage, and thus are not flying around like Mayflies and such. Rather, they’re present in the water constantly, year round. It’s due to this constant presence that crustaceans of all sorts are most important when other aquatic prey species for trout are not: late fall, winter, early spring. Scuds and sow bugs on the Madison aren’t quite as prolific as those on other regional rivers such as the Missouri, but they are still important for the trout diet on the Madison, nonetheless.


Scuds feed on vegetation and decaying detritus. Whenever the fly angler finds patches of weeds in the Madison or Ennis Lake, you can bet scuds and sow bugs are present and worth your attention. This typically occurs the closer one gets to Ennis Lake, where water warms, slows, and vegetation thrives. They usually occur in sizes from #10-16.


Crayfish are omnivorous, eating and scavenging on just about anything that presents itself to them including detrital vegetation and animal matter. Although Crayfish live in all water types, they are more abundant in warmer, slower river reaches where conditions are easier to get around in. Again, this is typically the type of water encountered closer to Ennis Lake. Crayfish can get extremely large near Ennis Lake. It’s not uncommon to see some approaching 6-8” long. Trout are keen to seek out this delicacy, and often times I’ll find Crayfish with their tails eaten off. Crayfish are nocturnal so one should place slightly more emphasis on fishing these imitations at dawn and dusk.


Aquatic Worms


Worms. One of the most ubiquitous aquatic prey species to trout in rivers throughout the world. The Madison River is no different and they are quite abundant, and I can tell you from my own guiding experience, that I rely quite heavily on the worm at times to fool trouts. If a bobber and a nymph are in your future on the Madison River, be sure to pack a San Juan worm or a standard Wire Worm in your arsenal.

Upper Madison River Macroinvertebrates

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