Parks' Fly Shop: Guide to Yellowstone Area Caddisfly Hatches, Yellowstone Hatches

Guide to Yellowstone Area Caddisflies

Caddisflies are probably the most important insects on most Yellowstone streams, at least to the many anglers who like to fish dry flies all summer long, especially on the larger, bouldery rivers and creeks, though the emergence of the Nectopsyche caddis on the Firehole has put caddis over the top on that river, as well.

The following guide includes general descriptions of the physical characteristics, flight times, and seasons of emergence for the most important caddisflies in the region. Suggested patterns are also given. Individual hatch guides for the most prominent streams in the area, with individualized season information and flight times, are given on the appropriate page in the Our Waters section of the Trip Planner.

My caddis entomology is not good, but it doesn't really have to be, as trout are usually less wary when eating caddis than when eating mayflies. Insects are listed in decreasing order of general importance. Please note that some insects are more important on some streams than others, however.

The most important things to remember about caddis emergences in general are: 1. they usually happen in the afternoon or evening, 2. caddis emerge more energetically than most mayflies, so rises are usually more violent, and 3. emergers and cripples are usually as good or better a bet than adult patterns.

Please contact us for more information on area hatches and the flies to match them.

The first portion of the following guide consists of an emergence table and notes. The second portion consists of longer descriptions of each listed insect.

Yellowstone Area Caddisfly Emergence Table

Table Key: X=primary hatch period, x=secondary hatch period, blank=no hatch
Name Description Emergence Time Emergence Month
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Tan Caddis (Hydropsyche) Tan to gray-brown, tan to gray-brown wings. #14-16 Usually afternoon to evening, often the best hatches are just at dark.           x X x x      
Olive Caddis (Bracycentrus or Mother's Day) Olive bodies, speckled tan wings. Midday to late afternoon.       x X x            
Nectopsyche (White Miller, Ginger Caddis) Creamy pale golden olive bodies, tan/ginger wings, VERY long antennae. Appears to be #14, but bodies are very small compared to wings. Usually mid-morning to mid- afternoon, sometimes earlier and later, especially when rainy/snowy.         x X x   X x    
Little Olive Caddis Brown wings, olive bodies, #18 Afternoon to evening.       x x x X x x      
Microcaddis (Glossosoma) Basically black or dark gray Afternoon. All over your boat and waders.           x X X        
Amber Caddis Tan wing, amber body, #16-18. Actually two types of bug, but they look the same. Evening           x X x        
Green Rockworm Caddis Green bodies, gray/black mottled wings. #12-16 Evening; the nymphs are far more important.           x X x x      
Great Gray Sedge Very large, brownish-gray overall. #10 Evening.           x X          
Travelling Sedge The big "moth" you see coming off of lakes. #8-10 2xl Afternoon and evening.         x x X x        

Discussion of Insects

Boldface type indicates fly patterns. Italics are used for scientific names.

Hydropsyche (aka Spotted Sedge)

Hydropsyche, various species.

The Speckled Tan Caddis is by far the most common summer caddis in our area. It hatches on all streams, large and small, though it is perhaps more common in faster stretches than slow. Look for it from mid-afternoon through evening. My favorite patterns are a Korn's SCHWARP or Flash SCHWAPF for the deep pupa, Lawson's Caddis Emerger for the emerging pupa, Tan X-Caddis for emergers/cripples, Tan Caddis Cripples, Tan Clacka Caddis (or even the attractor Coachman version), and Spent Partridge Caddis. With the exception of the Nectopsyche, the Travelling Sedge, and the Great Gray Sedge, you can plug the same patterns in the appropriate color (or just a #12 Coachman Trude) for every caddis on this list.

Olive Caddis (Mother's Day Caddis, Grannom)

Bracycentrus, various species.

THE hatch on the Yellowstone in the spring. Though the BWO, even the March Browns now, and the streamer fishing are more consistent, the week or so right before the high-country snowmelt hits in early May is when to be here if you want caddis up your nose, in your clothes, and in plenty of fish. In most respects this insect resembles the Hydropsyche, with the key difference being its darker body. Key patterns are the same, though we fish attractor dries even more for this one, because they're more visible to both you and the trout when there are thousands of naturals on the water and the river is getting dirty with runoff. Also, don't neglect the pupa. McCue's Glasshead Caddis is a killer during this hatch. Drop it off a Trude or Clacka and you're good.

Nectopsyche (White Miller)

Nectopsyche, species uncertain.

This is the one you MUST be ready to imitate if you're on the Firehole in June or September. Really heavy hatches of this "moth" really drive the fish crazy, especially since the behavior of the insect is to skitter along just above the surface of the wate. It is also present on the lower Gibbon and Madison, but nowhere near as important on these rivers. The bug is pale tan/ginger, with a creamy golden olive body. Pupae look white or cream. The key diagnostic for this fly is its long antennae, easily twice the body length.

Starting from the emerging pupa, you want our White Miller Soft Hackle, Ginger Clacka Caddis, Blonde Palmered CDC & Elk, and a few White Miller Cripples. Blue Ribbon Flies in West Yellowstone sells a different soft hackle and an identical cripple, as well as a couple other patterns that I'm sure also work. As far as I know, we are the only shops that sell patterns specifically for this bug. Unless you're getting a wholesale catalog I'm not, commercial patterns do not work to match this insect. We tie every imitation of it we use ourselves.

Little Olive Caddis

Lepidistoma pluviale.

This is the smaller major summer caddis. It has a darker brown wing and an olive body. On the Yellowstone the trout typically seem to prefer the Hydropsyche when they can get them, but this one is quite important on the Madison, and in June I've seen this bug hatching in overlapping waves with the White Millers on the Firehole.

Microcaddis (Little Black Caddis)

Glossosoma montana

This is the tiny black caddis that stains the seat of your pants when you sit down on them in the driftboat. They crawl all over the sides of the boat on the Yellowstone, but the fish seldom eat them. Black Henryville-types are what we use.

Amber Caddis

Arctopsyche and Helicopsyche

More important on the Madison and to a much lesser degree the Firehole than in the northern part of YNP. The key is the bright amber body. Otherwise they look more or less like a small to very small Hydropsyche.

Green Caddis (Rockworm, Rhyacophila)

Rhyacophila, a couple species.

This critter is one of the reasons chartreuse works. They roam around the bottom without a case, picking off smaller bugs. The larvae are generally MUCH more important than the adults, though I've seen the fish feeding on them on the Yellowstone and Madison. The larva is what Bob Jacklin caught the monster brown on "Between the Lakes" on the Madison with a few years ago.

Great Gray Sedge

Arctopsyche grandis

This large, brown or to grayish tan, rare caddis hatches on the Yellowstone, Madison, and Gardner in July. It's a big, imposing fly, best imitated by a Stimulator, large Goddard Caddis, or even a small Letort Hopper. There's a good chance fish take attractors like Turck's Tarantulas as this fly, since, though it's rare, it makes a good meal.

Travelling Sedge


When you see vee-wakes cutting across the surface of Trout Lake or other area lakes, and either a robin dive-bombing the wake or a big trout chasing it, you're seeing a pupa of this bug getting ready to pop. The pupae swim energetically towards shore before emerging, because the adults are so large they make easy pickings for birds if they try to emerge directly through the surface. Fish a large Tan Woolly Worm, Letort Hopper, or Sparkle Pupa on a slow sink tip and strip quickly. Whammo! If you hit it right, this will give you an evening of fishing you'll never forget.


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