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Angling Entomology: Six Hatches for Wisconsin

There are certainly more than six hatches but to keep things simple, these are the hatches that I think are worth chasing in Wisconsin. Why six? I have no idea but I wrote in earlier angling entomology posts that an angler should really learn five or six hatches that occur in their area to increase their success. Earlier I presented five hatches for the Driftless and there is a bit of overlap with the six I present here.

Bug net over a fishing net
A "bug" net that goes over a fishing net is a quick and simple way to see what is drifting or hatching and it can be used as a small kick net. Too bad I lost that net...

These are my six choices. Your mileage may vary. Click on the common name to link to that section, the scientific names link to pages.

In my experiences, the best hatches I have experienced in Wisconsin have been on northern Wisconsin freestone rivers like the Wolf River and on the streams of the Central Sands region. I covered the Grannoms and BWO's in the post about five Driftless Area hatches so I will give them less treatment here.

The Hex

The Hex is probably the best known and most enigmatic hatch in the Midwest. It is not my favorite hatch - I like to see what I am doing - but I totally understand why many anglers are hex-addicts. Anyone that has fished this hatch has stories to tell. Odd stuff happens at night, mid-thigh deep in a trout stream. You catch bats and birds, have beavers or otters scare the shit out of you, you may get carried away by mosquitos the size of hummingbirds, or any number of unexpected events may happen. You never know when you fish at night. You may catch the largest Brown Trout you have ever caught - you just don't know!

Image by John Sullivan, on the National Weather Service Tracking Mayflies page (2017 hatch)

What draws anglers to the Hex is that it is a massive hatch (or at least it can be), it is probably your best chance for a trophy fish on a dry fly, and the hatch is a tradition, a spectacle for many anglers. In much of Wisconsin, it is the hatch that many anglers look forward to all year. Hexagenia limbata (TroutNut link) is the hatch most are referencing by shortening it to "Hex" but there are other Hexagenia species - H. bilineata, H. atrocaudata and H. rigida and a few other species and Litobrancha recurvata that used to be classified as a Hexagenia species. Hexes - of several species but particularly H. bilineata - hatch so heavily on the Mississippi River that the National Weather Service tracks them by radar.

Impressed yet?

Hexagenia are burrowing mayflies that are filter feeders (collectors) as nymphs. They create a "U-shaped" burrow in the stream substrates which limits their distribution to streams with relatively solid (non-collapsing) and stable (non-moving) substrates. For the angler, the nymphs are unimportant until maybe a couple of hours before the hatch when the "wigglers" begin to leave the safety of their burrows and swim to the surface to hatch into the aerial sub-imago (dun) stage. It is difficult to put an exact time on when to expect this hatch as it is dependent upon not only water temperature but also air temperature and humidity. Fox Valley TU's Central Wisconsin hatch chart puts the heaviest emergence in early June, John Simonson's (WiFlyFisher) hatch chart for large northern rivers (Namekagon, Brule, White, Wolf) highlights late-June and early-July as the peak, and Patrick Hager who built his hatch chart from many years of observation on the Wolf River shows a similar late-June / early-July peak. The earliest emergence was June 7th and the latest was July 21st. Quite often, they seem to pick the warmest, most humid evenings to begin hatching. The hatch may last for a week or two but be rather hit or miss depending upon the weather. A cool evening or rainfall often halts the hatch until another night.

Hex adult
A not so spectacular photo of a Hex that is "chilling out" during the day and will return to mate during the evening.

While you can fish the wigglers with nymph pattern or even just a yellowish woolly bugger before the hatch, most anglers get to a spot and tie on a dry fly while they can still see. I have seen them begin to hatch at dusk but on most evenings, the hatch begins after well after dark. I have heard stories - but have never experienced for myself - a daytime emergence on particularly overcast days. My best success fishing the hatch was been with an emerger pattern as the nymphs are rising from the bottom and molting to their sub-imago (dun) stage and when the spinners (imago) return to the stream to mate and lay eggs. These "bugs" are large - I would start imitations at an inch (without tails) and tie them to nearly 2 inches. Being huge flies, fly tiers have devised about a gazzillion different fly patterns and most serious Hex anglers have their own personal favorites. And because they are large bugs, it gives tiers a lot of potential for creativity...despite the fact that their flies will be cast in the dark to fish that are probably only seeing silhouettes and sensing these big bugs through their lateral lines. But that is a lot of fly tying - it is a creative endeavor.

Below are a range of fly patterns - beginning with nymphs and ending with spinners - that you might consider. Links are to videos of the fly being tied.

For more about the hex hatch, see articles by Gink and Gasoline,, Hatch Magazine, and Streamside Orvis.

Brown Drakes

Brown Drakes (Ephemera simulans) are largely a hatch of large, freestone rivers. In Wisconsin, this means the Bois Brule, Namekagon, Wolf Rivers among others. These too are large "bugs" - not as large as the Hex but large for mayflies. Brown Drakes are typically imitated on a #8 or #10 hook, a bit smaller hooks for extended body flies. And like the Hex, these are a another burrowing mayfly but they tend to occur in sand and smaller gravel whereas the Hexes prefer finer substrates (silt and small sand). Fox Valley TU's Central Wisconsin hatch chart gives their peak in the first week of June and the hatch may extend for some time after that. Further north in Wisconsin, John Simonson (WiFlyFisher) shows the hatch happening over the first three weeks of June and Pat Hager has the peak of the hatch in the first two weeks of June with the earliest observed emergence on June first and the latest on the 14th of the month.

Above - images from the Wolf River including some flies and anglers from the river. For more information, I have written posts on the Flies of the Wolf River and another post on Mentors that featured George Close.

The drakes are typically a late evening hatch - generally the last hour before dark into the dark is prime time to be on the water. In my experience, it is probably the spinners that the angler is often imitating but they are fairly hardy bugs. Thus they can be imitated with standard upwing patterns as well as spent wing spinner patterns. But before we get to the spinners (imagos), let's start with the nymphs. Again, they are burrowers so look for them in stable substrates - mostly in pools and slower current areas with coarse sand and small gravel. They remain in their burrows for about a year (on occasion two years) until they emerge. As such, they are not readily available to trout except if their burrows get scoured. However, when they emerge, the nymphs will actively swim from their burrows to the surface and can be imitated with nymphs and wet fly patterns.

Brown Drakes typically emerge an hour or so before dark and the spinner fall may last an hour or more after dark. Personally, this hatch means a chance to fish some large dry flies when you can sort of see them unlike the Hex where you have nearly no chance of seeing your fly. My personal favorite is the Close Carpet Fly, a pattern my great uncle created for the Wolf River's great Brown Drake hatch. They are a pretty "stout" bug so the spinners often have upright wings but you can also tie flies like the Carpet fly with spent wings. Drakes tend to be one of the more abbreviated hatches; here today, gone tomorrow. But when you hit them right, they are a great hatch and one that is well worth chasing. I try at least ever few years to hit them on one of northern Wisconsin's larger trout rivers to fish this hatch - usually successfully.

Some fly patterns to imitate brown drakes, from nymph to spinner.

Some other more comprehensive links to tying for and fishing the brown drake hatch: Matching the Drake Hatch, WI Fly Fisher Brown Drake Patterns, and my own Flies of the Wolf River which included patterns for Cap's Hairwing, Close Carpet Fly, and Talasek's Killer (wet fly). Searches do not find a lot of patterns specific to brown drakes but patterns for the closely related green drakes (E. guttulata) and the European green drake or often simply called, "the mayfly" (E. danica) can easily be adapted to be brown drake imitations.

Sulphur Mayflies (Ephemeralla dorothea)

Sulphurs might be my favorite Wisconsin hatch but sadly, I have not fished a good sulphur hatch in the past five years, maybe more. It is not that the sulphurs are gone from Wisconsin - in many places it remains one of the best hatches - but I have not seen them in the numbers I used to on the Driftless streams I fish. That was a lament for another post (Aquatic Insect Declines?). This used to be the best mayfly hatch in the Driftless and the sparkle dun quickly became my favorite fly for how well it worked for this hatch and other mayfly hatches.

West Fork Kickapoo River
It is sulphur time - expect to fish them the last hour before sunset until you can no longer see.

The taxonomy behind what is a sulphur mayfly and Ephemerella spp. is a bit of a mess. Here in Wisconsin, we tend to think of the hatch as Ephermerella dorothea dorothea, often called a Pale Evening Dun (PED) as well. In other places, the Pale Morning Dun (PMD; E. dorothea infrequens) was formerly E. infrequens and not a subspecies of E. dorothea. And I do not seem them often here in Wisconsin but in Pennsylvania, I came across what were locally referred to a "yellow sulphurs" and "orange sulphurs" which earned their names based on the dun's wing colors. As best as I can figure out, these two "other sulphurs" are probably what were once referred to as E. rotunda, E. invaria, Epeorus vitreus, and maybe some other species (??) but what the hell they are now called, I am a bit less than sure. But who cares? Have some sulphur colored mayflies ranging from #12 to #20 with the bulk of them being #16 and #18 and you are probably just fine.

Sulphur mayfly
A sulphur mayfly from West Virginia's Elk River. This is a great hatch in much of the Eastern United States.

For the purposes of this post, I am going to consider sulphur mayflies to be E. dorothea dorothea as that is the most abundant and widespread hatch in Wisconsin. As nymphs, they are crawlers meaning that they crawl on rocks and do not have the more flattened shape of the clinger mayflies. They are grazers, scraping algae and other small (mostly) photosynthetic organisms from rocks. They are often drifting and have a peculiar habit of "testing things out" before they hatch. They may move up and down in the water column a few times before deciding to hatch. For the angler, this means a nymph - such as a pheasant tail nymph - or a wet fly - such as a soft hackle pheasant tail - fished actively through deeper and slower riffles, through runs, and particularly through pools can be very effective.

Many different sources talk about what a perfectly behaved mayfly species they are for the dry fly angler. They often ride on the surface for some distance to dry their wings, they often "get stuck" in their nymphal shucks, and both the males and female spinners will return to the stream, usually around dusk. Caucci and Nastasi in Hatches II talk about them as a "blizzard hatch" that can very difficult to figure out. Swisher and Richards in Selective Trout call them one of the most pleasant hatches of the season and I would have to agree.

Sulphur mayflies prefer to hatch in slower water so look for them along the edges of runs and in pools. Because of this habitat preference, trout can be particularly selective which makes the hatch often equal parts exhilarating and frustrating. Trout can get selective for a particular stage of sulphurs so if your standard dry fly is not working, consider a lower floating (parachute, comparadun) and/or an emerger pattern. And the spinner fall is very dependable - look for clouds of spinners over pools, particularly where the riffle changes to a pool. There are any number of patterns that I have found effective here and I typically fish until I have had my fill as they will continue until at least a half hour after dark much of the time.

Wolf River, WI
View from the Close family cabin on the Wolf River, were I first fished this hatch up in "The Oxbow" with George Close.

Look for sulphurs to hatch in late-May through the middle of June. Fox Valley TU's Central Wisconsin hatch chart puts the peak of the hatch in mid-May through the third week in June. In the Driftless, the are maybe just a bit earlier - I think of mid-June as the end of the hatch. In Northern Wisconsin, John Simonson (WIFlyFisher) lists Epeorus vitreus - quite a larger crawler mayfly as sulphurs in addition to the E. dorothea dorothea and E. invaria hatches. He sees the smaller sulphurs in mid-May through the first week in June and the larger E. vitreus hatches just a bit later (late-May through mid-June). And on the Wolf River, Patrick Hager sees them peak in early June with the earliest emergence on May 28th and the latest into July (July 7th).

Videos for sulphur fly patterns, from nymphs through spinners.

And lastly for the sulphurs, some other sources of information are: Fishing the Eastern Sulphur hatch, Fly Fisherman Magazine on the South Holston River (TN), Orvis - Covering the Sulphur Hatch From Top to Bottom, and I am sure you can find others. It is one of the east's best hatches.

They are the only caddis that made this list even though I fish caddis much more than I do mayfly imitations. Many of the caddis hatches seem to be less concentrated - they hatch over a long period of time but in lower densities. The Grannom (Brachycentrus) hatch is more condensed - typically it occurs for a couple of hours midday and it might last for two weeks in good and fishable numbers. In the Driftless, I look for them around the middle of April, generally on a warm day. Grannoms are sometimes - I think fairly mistakenly - called black caddis.

Above, Tom Lager's excellent presentation on the Grannom caddis for Fox Valley TU.

I covered the Grannom hatch in more detail in the Angling Entomology post on Driftless Hatches - go there for more details on their biology. What I do want to add here is a bit about the hatch outside of the Driftless Area. Fox Valley TU's Central Wisconsin hatch chart has the Grannom hatching over a three week peak that includes the last two weeks of April and the first week of May. They also list them as #14's and #16's, I more typically think of them as #16's and some on either side (#12 or #18) of that #16 hook. Further north in Wisconsin, Patrick Hager has the hatch peaking in late May with the earliest emergence in the third of May and the latest well into June (June 14th). This is pretty typical for Wisconsin hatches as they progress from southern Wisconsin northward much like a temperature dependent hatch may begin downstream and work its way upstream as that part of the stream warms.

Some flies to imitate the Brachycentrus hatches - with links to videos:

Again, I covered the Grannom hatch in more detail in the Angling Entomology post on Driftless Hatches - go there for more details on their biology.

Ephorons or White Mayflies (Ephoron leukon)

I debated including this hatch. Timing and the possibility for incredible numbers of "bugs" is the reason that this hatch was included. I might have chosen Tricos instead. They are more widespread and last longer than Ephorons but they are a size #18 on the large side and more typically a # 20 or #22 and depending upon the time of the year, you have to get up pretty early to catch a proper spinner fall. And I can not tell you how many times I have seen balls of trico spinners rising and falling in unison above a riffle on to have the wind kick up and have they disappear to try another day. When white mayflies are hatching, they tend to be fairly dependable so long as the night doesn't get too cool, too fast.

Smallmouth Bass
White mayflies can bring up some pretty good smallmouth bass too.

White mayflies are an evening, mid- to late-summer hatch of relatively large mayflies (#14) which is a welcome sight after a month or two of small mayflies and spotty hatches. This hatch is maybe a bit more geographically limited than some of the others, at least on trout streams. Ephorons are often a great hatch on Smallmouth Bass rivers and is quite famous on places like Pennsylvania's Susquehanna River (link to a news story). Some of Wisconsin's great Smallmouth Bass rivers have sizeable white mayfly hatches and you can catch them on what for bass seem like tiny dry flies or just use a white popper or bug and you should get into them. There are also tales of catfishes gobbling up rafts of mayflies and being caught on surface flies.

Ephorons are another burrower, so like most of the others (Hex and Brown Drake, above), they are not available as nymphs for much of their lives. Unlike other mayfly nymphs, they do not drift often or get dislodged by the current. What makes the Ephoron hatch so unique is that their transition from dun to spinner (subimago to imago) occurs so quickly. Very often you will see male Ephoron spinners carrying their trailing shuck and I have often had luck on patterns with a trailing shuck. Very often it is the spinners that anglers are imitating as the transition from nymph to dun occurs rapidly unlike some of the mayflies that hatch in cooler air and water temperatures where the transition is often slower.

In my experiences with this hatch, the best fishing occurs after sunset and lasts for an hour or so after dark. So get into position in a good relatively slow water area and watch for bugs. Fishing a nymph and stripping it and fishing downstream so it rises towards the surface can be good before sunset. Once the bugs really start hatching, thinks happen pretty quick. Duns and spinners are quite similar but as mentioned, often the spinners will be carrying the shuck of the dun. My favorite fly for this hatches is a Close Carpet Fly tied in white. Since you are going to be fishing it through the dark, pick a fly you like and tie it on a heavy tippet and hope not to have to change it.

This is a late summer hatch. I think of them from mid-August into September. As such, water temperatures can be an issues particularly on the lower ends of trout rivers where the right silt accumulates to support the nymphs. Rarely is this a hatch of headwater reaches because the correct habitat is unlikely to exist. It is however a hatch on many warmwater rivers so the transition zone where both Brown Trout and Smallmouth Bass overlap are often prime places to find a good Ephoron hatch. Fox Valley Trout Unlimited hatch chart has the peak of the hatch in the last two weeks of August and the first week of September. John Simonson (WI Fly Fisher) has the peak hatch in the first three weeks of August.

Some flies - with links to videos for tying these patterns.

Blue-Winged Olives (BWO; Baetis and others genera)

In comparison to the hatches above, BWOs occur over a much larger portion of the angling season. In part that is because it is not a single species or even a single genus that make up this hatch. When experienced anglers think of a BWO kind of day, they are thinking of an overcast, drizzly, or light rain day - most likely an afternoon but they can hatch earlier in the day. This is another hatch I covered in the Driftless hatches so I will give it less attention here.

A gorgeous fall day in the Driftless with a good friend - does not get much better.

As mentioned above, this hatch - or really series of different hatches all grouped into BWO and tiny BWO - occurs across nearly the entire season. Your BWO imitations should range from a size #14 on the large side down to as small as you care to tie and/or fish on the small side. To me, a #16 is large and #18's and #20's are more typical sizes I fish. I have some smaller (#22 and #24) imitations but they are not a ton of fun to fish for me. If I have to fish something that small, I am probably fishing it behind a larger dry fly. Patrick Hager lists the hatch beginning as early as March 12th and lasting through the end of the season along the Wolf River. John Simonson's (WIFlyFisher) mayfly hatch chart for northern Wisconsin has a similarly prolonged hatch but lists BWO"s as absent in July and August. And Fox Valley TU's Central Wisconsin hatch chart lists BWO's a a hatch that occurs all year long with peak emergences in April through mid-May and again in the fall (last two weeks of September and first week in October) and they suggest #18 and #20 flies. This mirrors my experience in the Driftless.

Some flies - with links to videos for tying these patterns.

As with the Grannom hatch, I covered the BWO hatch in the Angling Entomology post on Driftless hatches and you should go there for greater detail. And visit any number of other articles on how to fish a BWO hatch such as Hatch Magazine, Fin and Feathers, Frying Pan Anglers, and Headhunters Fly Shop on Pseudos.


Depending upon where you live and fish in Wisconsin, these may or may not be your six hatches. Three of the mayfly hatches - Hex, brown drake, and Ephorons - tend to be a bit more limited in their distribution. Each of them are worth traveling to go fish if you have not. The other three hatches - sulphurs, BWO's, and the Grannom caddis are widespread.

These are my choices - I would be interested in knowing where you fish and what your six choices of hatches would be. I might have removed the Ephoron hatch and replaced it with a trico hatch. It was tough leaving the Hydropsyche caddis off the list but I figure most of us think mayflies if we are going to chase hatches. Give me your six hatches in the comments.

Wisconsin Hatch Charts

Driftless Wisconsin Hatch Chart (one I did many years ago; Silver Doctor Fly Fishing)

Websites for Angling Entomology

YouTube Videos

Tim Cammisa - Stream Sample with Entomologist Matt Green - Part One and Part Two


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