Intro to Montana Caddisfly Hatches

Caddisflies, tent-winged insects somewhat resembling moths, are probably the most widespread stream-dwelling insects in the Yellowstone area, especially in the summer when the most tourists are here. Montana caddisfly hatches take place on all area streams, big and small, and probably account for a higher percentage of a trout’s diet than mayflies on all streams except flat meadow streams and rivers. On marquee rivers like the Yellowstone and Madison, they certainly predominate.

With that said, Montana caddisfly hatches don’t captivate anglers as well as mayflies. Why? Because they seldom hatch in as concentrated a fashion as mayflies or encourage the trout to rise in as technical/spooky a manner. This means that caddis hatches tend to get fish feeding, but not feeding consistently or spookily. Instead of picking one trout and changing flies five times before it strikes, as you might do during a mayfly hatch, you instead fish a generic caddis pattern or even an attractor dry fly that looks vaguely like a caddis, cover a lot of water, and pick up fish that you may not have known were even feeding before they ate your fly.

There are exceptions to this rule, of course. Evening summer caddis hatches on all but the smallest and/or steepest area rivers can get good numbers of trout rising in a small area, fish that only want one specific fly pattern, the White Miller or Nectopsyche caddis on the Firehole is probably the most consistent and most frustrating hatch on the Firehole River, and the fabled Mother’s Day Caddis hatches on the Yellowstone and Madison Rivers can produce 100-fish days, but only if you have the right bugs.

Most of the time, however, Montana caddisfly hatches do not require anglers to get too specific. A relative handful of similar patterns will usually interest at least a few fish regardless of what type of caddis are hatching. One big reason for this is that caddis are “busy” insects. Whereas mayflies ride gently and gracefully down the river before taking off and flying away, caddis are active. Their pupae swim energetically to the surface, bust through, and fly away moments after reaching the film, without taking time to dry their wings. Adult caddis buzz frenetically in circles just over the water surface. Egg-layers dip and bounce to the water time and again, fluttering like moths. Some caddis even dive back underwater to lay their eggs.

All of this means that trout are far, far more prone to chase caddisflies than mayflies, or any other insects. If you see trout making large splashes or even jumping clear out of the water, odds are they are taking emerging caddisflies. With such an aggressive mode of feeding, trout don’t have time to investigate caddis as thoroughly as mayflies. If your fly is about the right size and shape and flutters like a caddis, odds are they will take it like one.

In general, Montana caddisfly hatches are most common during early summmer, with hatches petering out for the year on most waters by mid August. You might still see caddis hatching after this, but they aren’t the staple food source they are earlier in the summer. The main exception is the Firehole River, where White Miller caddis are one of the two main insects into early October. Caddis also hatch in May just before runoff on the Yellowstone and Madison Rivers.

Except early in their emergence cycle, when morning hatches may occur particularly on the Firehole, caddis hatches are most likely either around midday or in the evening, with egglaying taking place in morning or afternoon. Since caddis live several days, unlike mayflies, there will almost always be a few caddis visible during the daylight hours, often tucked up under trees or brush in the shade, even if no hatch is underway. Because of this, it makes sense to fish caddis-style attractor dry flies or even dedicated caddis patterns throughout the day, particularly on rougher freestone rivers like the Yellowstone, Gallatin, Gardner, Boulder, Stillwater, and many small streams.

Yellowstone and Montana Caddisfly Hatches Chart

The following table covers important Yellowstone and Montana caddisfly hatches region-wide, from the most common and important insects to the least. Note that this is a general chart. Crucial insects on one body of water might be rare or even absent in others. Check the appropriate page under the Our Waters menu above for hatch charts specific to given bodies of water.

Also note that caddis are generally harder to identify than mayflies down to the species or even genus level. Therefore, there are actually a lot more caddis in the region than I’ve noted below. As long as you have flies to match the noted insects, you will be set up to match all the less-common bugs, as well.

yellowstone and montana caddisfly hatches chart

Important Note on Caddis Patterns for Area Rivers and Streams

As you have hopefully already noted, I suggest trying attractor dry flies when matching area caddisflies. This is particularly true during the summer, when many different species of caddis, both emerging and egg-laying, as well as other “downwing” insects may be present. If you are unsure which Montana caddisfly hatches are underway or which “specific” pattern to try, I suggest trying one of the following patterns. You’ll be surprised how often the nonspecific attractor dry flies that look generally like caddis but not like any one in particular will work as well or better than a more-imitative pattern.

The first five patterns are dries. The second five are subsurface flies. If you’re unfamiliar with a sepcific fly, Google it. It is probably a pattern developed locally, including by one of our guides, tiers, or friends.

  1. Peacock Clacka Caddis, #12 to #16
  2. Pink Clacka Caddis, #12 to #16
  3. Coachman Trude, #12 to #16
  4. Tan Butch Caddis, #12 to #16
  5. Pearl Spent Wing Caddis, #14 to #16
  6. Bead, Hare, and Copper, #12 to #16
  7. McCue Pupa, #14 to #16
  8. Soft Hackle Hare’s Ear, #14 to #16
  9. Gut Instinct, #14 to #16
  10. Brown Bird of Prey, #12 to #16

Discussion of Specific Montana Caddisfly Hatches

Note that many caddis are known equally by assorted common names or by their Latin genus names, hence the long headings.

Tan or Brown Caddis (Spotted Sedge or Hydropsyche)

Tan Caddis, often called Brown Caddis, Spotted Sedges, or by their Latin genus Hydropsyche, are the predominant caddis in the entire region during the summer months. They are size-14 or size-16, with tan, gray, or brown wings, often showing some darker spots (hence the name) and a paler tan or light brown body. Depending on the water in question, they may be present anytime from June through about Labor Day, with the heaviest numbers usually occurring on freestone rivers beginning a week or ten days after the water drops out of runoff and continuing for about a month.

Hatch activity primarily occurs in the evening. The heaviest and longest-lasting hatches occur when the weather is warm but overcast by midafternoon, which prompts the hatch to begin much earlier than usual. If it’s hot and sunny, the hatch may not begin until near dark. Egglaying activity takes place either early in the morning or sometimes in the hours before the evening hatch. All in all, there may be caddis of this species present through enough of the day that fishing a caddis-style attractor dry fly such as one of those in the list above is often a good bet all day long. This is particularly true if you are going for numbers of fish rather than large fish.

Good patterns to match this insect often do not need to look precisely like it, particularly dry flies. This is because these bugs are most likely when the water is still relatively high, fast, and a bit off-color. Peacock-bodied or pink-bodies caddis patterns are often just as effective as tan ones. Coachman or pink Clacka Caddis, and Tan Butch Caddis are our favorite high-floating dries which primarily suggest emerging caddis. Tan Partridge Caddis and tan or pearl Spent Wing Caddis suggest egg-layers or emergers that have drowned. Tan, Coachman, or pink Caddis Cripples split the difference.

Pupae and attractor nymphs that resemble pupae are also very important when these caddis are hatching. All of the subsurface patterns I mention in the list above save the McCue Pupa qualify. Fish them shallow or deep, either under an indicator with another, larger nymph, or under a dry, depending on where in the water column you expect the fish to be eating.

Olive (Mother’s Day or Brachycentrus) Caddis

The Mother’s Day Caddis, often called by its Latin genus Brachycentrus, create the marquee pre-runoff Montana caddisfly hatches on the Yellowstone, Boulder, Stillwater, and Madison Rivers in May, and extend into June on any waters that remain clear during the spring runoff. They are seldom important on spring creeks.

These insects are olive-bodied and have brown wings. They run slightly larger than the Tan Caddis on average, #14 more often than #16 (though #16 are also present). On the Yellowstone, these insects hatch in their millions over about a week in early to mid-May, often in such numbers that they form vast mats on the water surface in every eddy or foam patch. 100+ fish days are possible when the hatch is really good. The problem is that they hatch right at the onset of the spring runoff, when water temperatures crack about 50 degrees. Often we’ll get one solid day of fishing, one okay day when the river is milky-brown and rapidly going out of shape, and then watch the river turn to unfishable chocalate stew. So this is a very hard hatch to hit on the Yellowstone, and if you want to do it, you must be prepared for Plan B and Plan C if the Yellowstone turns too muddy to fish before or in the midst of the hatch. About May 7-10 is the most likely timeframe for the hatch on the Yellowstone.

On the Lower Madison, Firehole, Missouri, and other rivers, the hatch takes place over a longer period of time, with May 10 through May most likely on the larger rivers and the first week of June best on the Firehole. On these waters, the hatch is not as heavy but is more a sure thing to be fishable. Look for hatches to take place around midday extending until early evening on the Yellowstone, Lower Madison, and Missouri, but mostly take place from midmorning until early afternoon on the Firehole.

Subsurface pupae patterns are often your best choice when fishing this hatch, even when many fish are rising. By far my favorite is the McCue Pupa but olive Partridge Caddis Emergers are also good. Fish the pupa as a dropper behind a high-floating dry: Coachman Trudes or Clacka Caddis, or olive Butch Caddis or Missing Link Caddis. If the trout want a lower-floating dry (more common on the Firehole or Madison than the Yellowstone), use olive X-Caddis. All patterns should be #14 or #16, with the larger flies working best when the water is getting muddy, at which time even a #12 Coachman Trude might work.

White Miller (Blonde Caddis or Nectopsyche)

White Millers, which may more often be called Nectopsyche, are the most important single hatch on the Firehole River. They are present from the beginning of the Yellowstone Season in late May through June, and again from September into early-mid October. They are also present in the lower Gibbon River and the headwaters of the Madison River in Yellowstone Park, where they are less important. Elsewhere they are essentially nonexistent or at least so rare that they don’t interest the fish or anglers. This goes for everywhere, not just the Yellowstone region.

Because of their rarity beyond the Yellowstone region, all patterns to match this insect that I suggest were designed and are often still produced locally. These bugs appear white or cream from a distance, and seem to be quite large, but up close they have tiny golden olive bodies and white wings as adults, with extraordinarily long antennae. Their pupae are shimmering white, with an olive thorax. One common attribute of this insect is that it is busy: you will almost always find them skittering or skating over the water, either in the surface film or just above it, often along grass that overhangs the stream. For this reason, you should always keep your flies moving when matching this insect save when fishing cripple or egglaying patterns in slow water.

On the Firehole, hatches may occur at any time of day, but midmorning to early afternoon and early evening until sunset are most likely except late in June or anytime in June during low water years, in which case hatches may occur first thing in the morning. On the Madison and Gibbon, hatches are more likely on late June evenings.

Three categories of patterns to match this insect: pupae, high-floating adults, and low-floating adults. For pupae, White Miller Soft Hackles are the go-to fly, but trout will also eat a smaller Glasshead Pheasant Tail. Fish these either on a traditional wet fly swing in riffles and runs or as droppers behind a high-floating dry. Top high-floating dries are White Miller Clacka Caddis or Nectopsyche Iris Caddis and blonde CDC and Elk. These can be dead-drifted or skated, usually in fast water. If you see fish rising in slow water late in the hatch, opt for a White Miller Cripple to match crippled or egg-laying insects. Dead drift these. All patterns should be tied on short-shank #14 or #16 hooks with short bodies and extra-long wings to match the proportions of the real bug.

Green Rockworm (Rhyacophila)

Green Rockwroms or Rhyacophila are large, free-living, predatory caddis that are common in all freestone streams but seldom of interest to dry fly anglers. Instead, many nymph patterns match their larvae and pupae. Good patterns include some chartreuse or peacock herl elements, since these insects have a distinct green hue. Flies should be #10 to #14. Prince Nymphs are good enough imitations in most area waters, and also imitate many other bugs. These nymphs are reasonable choices through the summer.

Traveling Sedge

Traveling Sedges are the only common caddis in area lakes. They are also our largest common caddis, typically #8 to #10, with good patterns tied on 2xl hooks. They have gray, light brown, or tan wings and tan to pale olive-brown bodies. They are most important on Trout Lake, but can be found in private ranch lakes, Lewis and Shoshone Lakes, and Henry’s Lake southwest of Yellowstone Park, in Idaho. Hatches can occur from late June into early October, with the later dates only common on Lewis Lake.

Despite their limited range and importance, these caddis really excite both big trout and anglers when they hatch, because the insect’s habits make the trout respond very aggressively. The pupae are by far the most important stage of this insect. They swim aggressively towards the surface, then cut vee-wakes just below the surface before popping through the surface film and flying off. You will often see birds dive-bomb the wakes the bugs make, which are easily noticeable and actually look more like fish swimming just under the surface. To match this behavior, strip large pupa or even dry caddis patterns just under the surface, moving them quickly. Fish heavy tippets because strikes can be vicious. Hatches are most common in the evening, but may occur at midmorning as well. Good flies include the Henry’s Lake Caddis, tan Letort Hoppers, tan Woolly Worms, and large Goddard Caddis.

Giant Brown Caddis

Giant Brown Caddis, of an unknown species (they may even be adult Green Rockworms), hatch in moderate numbers in late June or early July on freestone rivers, for about two weeks. They almost always pop just as rivers become fishable post-runoff, in conjunction with the Salmonfly and Golden Stonefly emergences, which are what most anglers imitate at this time.

Because everybody else is matching Salmonflies, attractor dry flies approximating the size and shape of the Giant Brown Caddis make great “change-up” flies when any giant brown caddis are about. We have often done better (whether guiding or fishing on our own) matching the caddis rather than the bigger stoneflies, even when there are more stoneflies about, either because the fish have been stung too many times by fake stoneflies or simply because they are glutted on these large insects and want a smaller snack. The real insects have a prominent chocolate brown wing, and run #10 to #12, but our favorite patterns to match it are all attractor dries: Coachman Trudes, Walter’s Synth Double Wings, and small Turck’s Tarantulas.

Amber Caddis

Amber-colored caddis hatch in lesser numbers than Tan Caddis during high summer, perhaps running slightly later in the summer as well. There may be two or three species of these insects. All are #16 or #18, with paler wings than the Tan Caddis (usually light tan or ginger-amber), and bodies that are slightly gold-orange. Look for them in afternoon and evening, same as the Tan Caddis. Some years there are lots of these bugs, some years less. They are generally more important on the Madison River than on the Yellowstone or elsewhere. Match them with Amber Iris Caddis or Gingersnap Clacka Caddis.

Microcaddis (Glossossoma)

These are the tiny (#22 or so) black caddis that crawl on boats and the legs of wading anglers in massive numbers on the Yellowstone and Madison Rivers, usually in July. They are usually unimportant to anglers because there are so many larger food items available at the time. If you do believe the trout are eating them, any tiny black caddis dry should work. You might also try a black midge. Subsurface, #18 or #20 pink-bodied pupae or soft hackles may draw some strikes. The trout are more likely to eat these bugs on the Madison than elsewhere.

October Caddis

This giant (#8 or #10) orange caddis is among the marquee hatches in Western Montana, Idaho, and British Columbia. Unfortunately, there are very few in our area as we are farther east and south than their core range. Occasionally we see a handful on the Yellowstone, Madison, or Gardner River, or on Middle Creek which drains east from Yellowstone Park into the North Fork of the Shoshone River. We have never seen enough hatching for dry patterns to work. Orange pupal patterns with black hackle can work for fall-run browns, but whether they are taking the fly as a true caddis pupa or merely eating it as an irritant is an open question. Fish a big orange beadhead soft hackle if you’d like to try this method, either on a dead-drift like a nymph or on the swing. October Caddis pupae seem to interest our browns primarily from about September 15 through the first week of October.