RS2
Rim Chung's elegant emerger pattern imitates Baetis and midge emergers in the surface film. The RS2 is a year-round producer on the Missouri and Bighorn, where technical anglers target rising fish during midge and BWO hatches. The RS2, short for 'Rim's Semblance 2', is one of the most elegant and effective emerger patterns ever designed. Its sparse design features a beaver fur or Antron body, a split Micro Fibett tail, and a puff of CDC or web-like wing material that suggests the unfolding wings of an emerging mayfly or midge. The pattern sits in the surface film with its body submerged and its wing material visible above, creating a perfect silhouette of an insect caught in the act of hatching. On Montana's tailwater rivers, the RS2 is an essential pattern for technical dry fly and emerger fishing. During the prolific BWO and midge hatches on the Missouri and Bighorn rivers, trout often key on emergers trapped in the surface film rather than fully emerged adults. When you see trout rising with subtle, sipping rises but they refuse your dry flies, the RS2 is the answer. Fish it on 6X or 7X tippet with a drag-free drift, and prepare for the satisfaction of fooling highly selective tailwater trout on one of fly fishing's most refined patterns.
Pattern Details
- Type
- Emerger
- Seasons
- spring, summer, fall, winter
- Hook Sizes
- #18-24
- Hook Type
- Fine-wire dry fly hook or emerger hook
- Tying Difficulty
- Intermediate
- Imitates
- Baetis (BWO) emergers and midge emergers (Chironomidae)
Recipe & Materials
- Hook
- TMC 101 or Tiemco 2487, sizes 18-24Shop
- Thread
- 10/0 or 12/0 olive or gray
- Tail
- Dun Micro Fibetts, split in a V
- Abdomen
- Beaver fur dubbing or Superfine, olive or gray
- Wing
- CDC puff or Antron yarn, gray or dun
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Technique & Presentation
The RS2 is designed to be fished in the surface film, not on top of it. Do not apply floatant to the body; you want it to sink into the meniscus while the wing material stays visible above the surface. A tiny amount of floatant applied only to the CDC wing puff will help it stay visible without lifting the fly out of the film.
Present the RS2 upstream to rising trout during midge or BWO hatches. The cast must be accurate and the drift must be drag-free; these are the non-negotiable requirements for success with this pattern. Use 6X or 7X tippet and a long leader (12-15 feet) to minimize the chance of drag. Watch the wing puff carefully; takes are often subtle, with the wing simply disappearing into a quiet dimple.
The RS2 is also effective when fished as a dropper off a more visible dry fly. Tie 18-24 inches of 6X tippet off the bend of a Parachute Adams or other visible pattern, with the RS2 trailing below in the film. This tandem rig gives you two chances to catch a rising fish and allows you to track the RS2's position by watching the larger dry fly.
History & Origin
The RS2 was created by Rim Chung of Denver, Colorado, in the 1970s. Chung, a Korean-American fly tier and angler, designed the pattern to imitate the small mayfly and midge emergers he observed on Colorado's South Platte River. The name stands for 'Rim's Semblance 2,' with the original RS1 being a slightly different design that Chung refined into the RS2.
Chung's pattern gained recognition through Colorado's tight-knit technical fly fishing community before spreading to other demanding tailwater fisheries across the West. On Montana's Missouri River, the RS2 became a standard pattern for guides working the technical hatches below Holter Dam. The fly's influence extends beyond its own pattern; its design philosophy of sparse, in-the-film emerger presentation has influenced an entire generation of emerger patterns.
Where to Fish This Fly
Missouri River
Central Montana
BWO and midge emerger
Bighorn River
Southeast Montana
Midge and BWO emerger
Frying Pan River
Roaring Fork Valley / Central Mountains
Deadly BWO and midge emerger; fish in the film or just below
South Platte River
Front Range / South Park
Deadly BWO and midge emerger; fish in or just below the film
North Platte River
Central Wyoming
Critical midge/BWO emerger for Grey Reef surface feeders
Green River
Southwest Wyoming
Midge and BWO emerger for clear tailwater fishing
Bighorn River (Wyoming)
North Central Wyoming
Midge and BWO emerger for the clear, slow water
Henry's Fork
Eastern Idaho
RS2 emerger for midge and BWO activity on the Ranch
Silver Creek
Central Idaho / Sun Valley
RS2 emerger, arguably the most effective Silver Creek subsurface fly
South Fork Boise River
Southwestern Idaho
RS2 emerger, critical for midge and BWO surface feeding
Crooked River
Central Oregon
Outstanding BWO emerger. Deadly during hatch transitions.
Metolius River
Central Oregon (Cascades)
Subtle emerger for selective fish during BWO hatches
Owyhee River
Southeastern Oregon
Midge and BWO emerger. Technical but highly effective on educated fish.
Rocky Ford Creek
Central Washington, Grant County
RS2 as midge and BWO emerger, deadly in the film
Hat Creek
Northern California / Shasta County
RS2 for BWO and midge emergers
Fall River
Northern California / Shasta County
RS2 for BWO and midge emergers
East Walker River
Eastern Sierra / Mono County
RS2 for BWO emergers spring and fall
Hot Creek
Eastern Sierra / Mono County
RS2 for BWO and midge emergers; fish in the film
East Walker River
Western Nevada / Lyon County
Spring/fall BWO emerger, fish in surface film
San Juan River
Northwestern New Mexico / San Juan County
Deadly BWO and midge emerger; fish in or just below the film
Colorado River at Lees Ferry
Northern Arizona / Coconino County
RS2 for BWO and midge emergences in spring and fall
Oak Creek
Central Arizona / Oak Creek Canyon
RS2 for fall BWO hatches, deadly in the film
Davidson River
Western North Carolina / Pisgah National Forest
Small emerger pattern for technical spring fishing
Tuckasegee River
Western North Carolina / Jackson County
Small emerger for selective tailwater trout
Nantahala River
Western North Carolina / Macon County
Small emerger pattern deadly in clear tailwater conditions
Watauga River
Northwestern North Carolina / Watauga County
Small emerger pattern for selective fish
Deep Creek
Western North Carolina / Great Smoky Mountains National Park
Small emerger for selective fish
Linville River
Western North Carolina / Avery County
Small emerger for technical fishing
South Toe River
Western North Carolina / Yancey County
Small emerger for selective trout
Grand Lake Stream
Downeast Maine / Washington County
RS2 in sizes 20-24 for selective salmon feeding on midges.
Mascoma River
Upper Valley / Grafton County
RS2 for selective fish during fall BWO hatches.
Battenkill River
Southern Vermont / Bennington County
RS2 deadly during BWO hatches fished in the film.
Dog River
Central Vermont / Washington County
RS2 for selective fish during BWO hatches.
Deerfield River (Upper)
Southern Vermont / Windham County
RS2 deadly during fall BWO hatches in clear tailwater.
Walloomsac River
Southern Vermont / Bennington County
RS2 for selective trophy fish.
New Haven River
Central Vermont / Addison County
RS2 for selective fish during BWO hatches.
Penns Creek
Central Pennsylvania / Centre County
BWO emerger for spring hatches
Spring Creek
Central Pennsylvania / Centre County
Deadly BWO and midge emerger; fish in the film
Spruce Creek
Central Pennsylvania / Huntingdon County
RS2 for BWO and midge emerger
Big Spring Creek
South Central Pennsylvania / Cumberland County
RS2 for BWO and midge emerger
Related Emerger Patterns
Sparkle Dun
Craig Mathews' emerger design sits in the film with a trailing Antron shuck, imitating a mayfly emerging from its nymphal shuck. Essential during PMD and BWO hatches when trout key on vulnerable emergers. The Sparkle Dun is one of the most important patterns to come out of the Yellowstone country fly fishing tradition. Craig Mathews designed it to fill the gap between a fully submerged emerger and a high-riding dun pattern. The result is a fly that sits in the surface film with a deer hair wing extending upward and a trailing Antron shuck dragging in the water behind, precisely imitating a mayfly that has broken through the surface and is shedding its nymphal exoskeleton. This is the moment when mayflies are most vulnerable, and it is the moment when trout feed most selectively. The Sparkle Dun has earned its place as a must-carry pattern on Montana's premier hatch-matching rivers. During PMD hatches on the Missouri and upper Madison, trout often ignore fully emerged duns in favor of the crippled and emerging insects caught in the film. The Sparkle Dun matches this stage perfectly. During BWO hatches in spring and fall, a size #18-20 olive Sparkle Dun can be the only pattern that produces when trout are locked into their feeding rhythm and refusing everything else.
BWO Emerger
A Blue-Winged Olive emerger pattern with a slender olive body and CDC wing. BWO emergers are critical during spring and fall Baetis hatches, particularly on overcast days when these tiny mayflies hatch in incredible numbers. The Blue-Winged Olive hatch is one of the most important and consistent hatches on Montana's rivers, occurring reliably in spring and fall when overcast skies and cool temperatures trigger mass emergences of Baetis mayflies. During these hatches, trout feed with extraordinary selectivity, often refusing adult dun patterns in favor of the emerging insects trapped in the surface film. The BWO Emerger, with its slim olive body and CDC wing, is specifically designed for this scenario. The pattern's design places it right in the feeding zone that matters: the surface film. The CDC wing provides just enough buoyancy to keep the fly suspended at the meniscus while the slender olive body hangs below, mimicking a Baetis nymph in the act of emerging. CDC (cul de canard) feathers are the ideal material for this application because their natural oils repel water without artificial treatment, and their soft, web-like structure provides a lifelike impression of unfolding wings. On the Missouri, Bighorn, and spring creeks throughout Montana, this pattern is essential equipment during every BWO hatch.
CDC Caddis Emerger
A soft-hackle style caddis emerger using CDC feathers for buoyancy and movement. Fish it in the film or just below during caddis hatches. The natural oils in CDC create a lifelike shimmer that trout find irresistible. The CDC Caddis Emerger bridges the gap between traditional soft-hackle wet flies and modern surface emerger patterns. Using CDC (cul de canard) feathers as the primary wing and hackle material, this pattern sits in or just below the surface film, perfectly imitating a caddis pupa ascending to the surface and beginning to shed its pupal shuck. The CDC fibers trap tiny air bubbles that give the fly a lifelike, shimmering quality, mimicking the gas bubble that natural caddis pupae use to propel themselves to the surface. On Montana's rivers, caddis emergers fill a critical niche during the prolific caddis hatches that occur from spring through fall. When trout are splashing at the surface during a caddis hatch but refusing adult patterns, they are often feeding on emerging pupae just below the film. The CDC Caddis Emerger presented in or just under the surface film is the solution. It is particularly effective on the Yellowstone during the Mother's Day caddis hatch, on the Madison during summer evening emergences, and on the Gallatin where caddis are a primary food source throughout the season.
Blue-Winged Olive CDC Emerger
The Blue-Winged Olive CDC Emerger is a deadly pattern designed to imitate the vulnerable transitional stage when Baetis mayflies are emerging from their nymphal shuck and breaking through the surface film. This critical moment in the mayfly lifecycle represents one of the most productive feeding opportunities for trout, and patterns that effectively mimic this stage often outperform both standard dry flies and subsurface nymphs during active hatches. Cul de Canard (CDC) feathers are the secret to this pattern's effectiveness. These unique feathers, taken from around a duck's preen gland, contain natural oils that make them extraordinarily buoyant and water-resistant. CDC creates a lifelike, translucent appearance in the surface film that perfectly mimics the wings of an emerging mayfly. The soft, mobile fibers also create subtle movement with even the slightest current, triggering strikes from selective trout. The BWO CDC Emerger excels during the peak of Blue-Winged Olive hatches, particularly when trout are feeding just subsurface on emerging nymphs rather than taking fully emerged duns. This often occurs during the initial stages of a hatch or in turbulent water where emergers struggle to break free from the surface. The pattern sits partially in and partially above the surface film, presenting a silhouette that trout find irresistible. Fishing this pattern requires delicate presentations with fine tippets (6X-7X) and careful attention to drag. The CDC emerger should be allowed to drift naturally without any tension on the leader. Strikes can be subtle—often just a slight hesitation in the fly's drift or a small dimple on the surface. During heavy BWO emergences on spring creeks and tailwaters from Oregon to Pennsylvania, this pattern can produce extraordinary results when nothing else works on ultra-selective trout.
Blue-Winged Olive Emerger
The Blue-Winged Olive Emerger is a versatile transitional pattern that bridges the gap between subsurface nymph and fully emerged dry fly. Designed to sit in or just below the surface film, this pattern imitates the critical moment when Baetis mayflies are transforming from nymphs to winged adults—a period of extreme vulnerability that trout exploit with focused feeding. What makes emerger patterns so effective is that they match the behavior trout actually observe during hatches. Research has shown that trout often feed more heavily on emergers than on either nymphs or fully emerged duns, particularly in smooth water where they can selectively target insects trapped in the surface tension. The BWO Emerger presents the segmented body of the nymph combined with the emerging wings, creating a silhouette that trout recognize instantly. This pattern excels during all phases of Blue-Winged Olive emergences, which occur throughout much of the year but peak in spring and fall. It's particularly effective during the middle stages of a hatch when the majority of insects are transitioning, and when weather conditions (cold, wind, or rain) slow the emergence process, causing insects to struggle in the film longer than usual. These are precisely the conditions when BWO hatches are most likely to occur. The BWO Emerger works across diverse water types—from the spring creeks of Pennsylvania to the tailwaters of Colorado and Wyoming. It can be fished alone on a fine tippet with careful presentations, or as a dropper below a buoyant dry fly indicator. The pattern's year-round utility makes it essential for anglers who fish technical waters where Baetis hatches provide consistent feeding opportunities even during winter months when other mayflies are absent.
Film Critic Emerger
The Film Critic is a deadly emerger pattern designed to imitate mayflies trapped in the surface film during the vulnerable transition from nymph to adult. Created by Wyoming guide Pat Dorsey, this pattern capitalizes on the fact that emerging mayflies often spend critical seconds suspended in the meniscus while their wings unfurl—a moment when they're helpless and highly visible to feeding trout. The Film Critic's low-floating profile and realistic silhouette make it devastatingly effective during mayfly hatches when trout focus on emergers rather than fully emerged duns. The pattern features a dubbed body that hangs below the surface film, a CDC wing that suggests the partially emerged wings, and a high-visibility foam post that allows anglers to track the fly while maintaining a realistic profile to the fish. This design perfectly mimics the natural emerger's posture in the water, with the nymphal shuck trailing below and emerging wings breaking through the surface. The pattern works for multiple mayfly species by varying size and color, including Green Drakes, Pale Morning Duns, and Blue-Winged Olives. Film Critic excels during selective feeding situations when trout refuse standard dry flies. During heavy hatches, trout often key on emergers because they're easier to capture than fully emerged adults that can fly away. The emerger's helpless position makes it a high-percentage target. This pattern's effectiveness is enhanced by fishing it dead-drift in the surface film, occasionally giving it a slight twitch to imitate the struggling insect. The pattern has proven effective across all Western waters, particularly in technical spring creeks and tailwaters where educated trout scrutinize their food carefully. South Platte River in Colorado, Wyoming's North Platte, Montana's Missouri River, Idaho's Silver Creek, and California's Hat Creek all see excellent Film Critic action. The pattern's versatility across mayfly species and sizes makes it an essential emerger selection for serious trout anglers fishing from spring through fall.