Midge Fly Fishing: A Beginner's Guide to Catching Trout on the Smallest Flies

Midge fly fishing is the practice of using tiny fly patterns (sizes #18 to #28) to imitate midges, the small aquatic insects that make up the largest portion of a trout's diet in most rivers and streams. Successful midge fishing comes down to three things:

• Matching the right fly to the midge life stage that trout are feeding on
• Using lighter tippet (6X or 7X) for a natural presentation
• Fishing at the correct depth in the water column.

In this guide, you'll learn what midges are, the three life cycle stages trout feed on, six proven midge patterns, two rigging setups, and the gear adjustments that make midge fishing approachable, even if you've never tied on anything smaller than a size 14.

This table shows the key basics of midge fishing to help you get started. Scan it quickly to match the right season, fly size, tippet, and best patterns.

What to Know	Key Details
Midges Definition	Small, non-biting aquatic insects (family Chironomidae) that trout eat year-round
Best Season	Year-round, but especially effective late fall through early spring
Typical Fly Sizes	#18 to #24 (some anglers go down to #26 or #28)
Tippet Range	5X to 7X fluorocarbon
Best Water Types	Tailwaters, spring creeks, slow pools on freestone streams
Key Patterns	Zebra Midge, Griffith's Gnat, Top Secret Midge, RS2

Midges go through four stages: egg, larva, pupa, and adult. Eggs aren't fishable, but the other three stages each have proven fly patterns that catch trout consistently.

1. The larva is a thin, wormlike form that lives on the stream bottom in silt and debris. Larvae range in color from red (often called bloodworms) to olive, cream, and black.
2. The pupa is the most vulnerable stage for trout feeding. Midge pupae rise through the water column toward the surface, and trout intercept them mid-drift. Pupae have a thicker middle section (the thorax) with visible wing buds forming inside.
3. The adult is a small, delicate insect that sits on the surface film after hatching. Trout sip adults gently, often barely breaking the surface.

Larvae and pupae call for subsurface patterns (wet flies), while adults call for surface patterns (dry flies vs wet flies is a distinction worth learning early). Identify the life stage you’re seeing on the water, then use this guide to choose the correct fly and presentation.

Life Stage	Top Patterns	Sizes	Where to Fish It
Larva	Zebra Midge, Brassie, Blood Midge	18 to 24	Near bottom, deep pools, slow runs
Pupa / Emerger	Mercury Midge, Top Secret, RS2, CDC Transitional Midge	18 to 24	Mid-column to just below the surface
Adult	Griffith's Gnat, Matt's Midge, Parachute Midge	18 to 26	Surface film, slack water, foam lines

Watch the water's surface for visual cues. If you see tiny insects hovering in a cloud above the water like dust, or small dark clusters of bugs sitting on the surface film, those are adult midges. If trout are rising with barely a ripple, they're likely eating pupae just under the film. No surface activity at all usually means trout are feeding on larvae near the bottom.

Midges hatch year-round in most trout water, making them fishable in every season, but they become the dominant food source from late fall through early spring when other aquatic insects go dormant. During the winter months, midges are often the only insect on the water.

Midges often hatch heaviest during the warmest part of a winter day, roughly 10 am to 2 pm. Plan your fishing around that midday window from late fall through early spring, and you'll hit the best action. In warmer months, early morning and late evening hatches pick up as well, but midges rarely shut off completely during daylight hours.

Finding the right water is half the battle. Once you’ve identified the right water type, the next step is selecting the correct life stage and fly pattern.

• A tailwater is a section of a river directly below a dam, where cold, consistent water releases create year-round midge habitat. Well-known midge tailwaters include Colorado's South Platte River, New Mexico's San Juan River, and Montana's Bighorn River (we cover these and more in our fly fishing destinations in the US guide).
• A spring creek is a stream fed by underground springs, producing clear, slow-moving water with silty bottoms where midge larvae thrive in high densities.
• On freestone streams, focus on slower pools, eddies, and backwater areas. Midges are less concentrated in fast riffles but still present throughout the system.
• In stillwater (lakes and ponds), midges (often called chironomids in stillwater fishing) produce exceptional fishing, especially during spring and fall when hatches stack up in the shallows.

Pro Tip: When scouting new water, look for smooth current seams and areas with a silty or sandy bottom. These are reliable midge hotspots regardless of water type. A quick streamside check of subsurface rocks for midge larvae cases can confirm you're in the right zone before you even tie on a fly.

The best midge patterns for trout cover all three fishable life stages, larva, pupa, and adult, and you only need about six flies to handle the majority of midge fishing situations.

Most fisheries biologists estimate that 80 to 90% of a trout's diet comes from below the surface, which is why subsurface midge patterns outproduce dries on most days.

The Zebra Midge (sizes 18 to 22) is a beadhead larva imitation with a thread body and fine wire ribbing, available in black, red, and olive. Fish the Zebra Midge near the bottom under a strike indicator. This pattern has fooled more tailwater trout than any other single fly in the last 20 years.

The Mercury Midge (sizes 18 to 22) is a pupa imitation with a glass bead that mimics the gas bubble forming inside a midge as it rises toward the surface. The Mercury Midge catches trout consistently during active hatches when fish are keyed in on rising pupae.

The Top Secret Midge (sizes 20 to 24) was developed by veteran South Platte River guide and fly fishing author Pat Dorsey. The Top Secret Midge imitates the emerger/pupa transition and has a proven track record on pressured tailwater trout that have seen just about everything.

The Brassie (sizes 18 to 22) is a weighted midge pattern with a copper wire body and peacock herl thorax. Simple, heavy, and effective in water deeper than 3 feet. When you need to get down fast, the Brassie is your fly.

The Griffith's Gnat (sizes 18 to 22) is a dry fly (a fly that floats on the water's surface) that imitates a cluster of adult midges. For such a small fly, the Griffith's Gnat is surprisingly visible on the water, making it a great "sighter" fly when fishing a two-fly rig.

The RS2 (sizes 20 to 24) is an emerger pattern that hangs in the surface film rather than sitting on top of it. Fish the RS2 when trout are sipping just below the surface and ignoring full dries.

The Matt's Midge / Parachute Midge (sizes 20 to 26) imitates a single adult midge trying to take flight from the surface. Fish it on 6X or 7X tippet for the most natural drift.

Rigging for midge fishing requires lighter tippet, longer leaders, and more precise depth control than most other fly fishing setups, but the adjustments are easy once you understand the basics.

Two rigs account for the majority of midge fishing success: the indicator nymph rig for subsurface larvae and pupae, and the dry-dropper rig for emergers during an active hatch.

Rig 1: Indicator Nymph Rig (Best for Larvae and Pupae)

Start by tying a heavier point fly (like a Brassie or beadhead Zebra Midge) to the end of your 6X tippet. About 12 to 18 inches below that fly, attach a lighter midge dropper using a separate piece of tippet. Position split shot (small removable weights) 12 to 18 inches above the point fly so the rig can sink close to the bottom.

Place the strike indicator (a small float that signals when a fish takes your fly) at one and a half times the water depth. For example, in 3 feet of water, the indicator should sit about 4.5 feet above the bottom fly.

Cast upstream, mend the line to eliminate drag, and watch the indicator for any pause, dip, or twitch. Light tippet breaks at 2 to 3.5 lbs of force, so set the hook with a gentle lift of the rod tip instead of a hard strip-set.

Rig 2: Dry-Dropper Rig (Best for Emergers During a Hatch)

Tie a visible dry fly (the Griffith's Gnat works perfectly) to your tippet. Cut a 10 to 14-inch piece of 6X or 7X tippet and tie it to the bend of the dry fly hook. Attach an emerger pattern (RS2 or CDC Transitional Midge) to the end of that dropper.

The dry fly acts as both a strike indicator and a second offering. When it dips or gets pulled under, set the hook.

Most anglers struggle with midges because they give up too soon. Slow down, watch the water carefully, and commit to fishing small for a full outing. When you hook trout on flies that most people can barely see, you can catch fish when others aren’t.

A handful of patterns from a nymph assortment and a few picks from a dry fly assortment will round out your midge box.

Stock up on proven patterns from Wild Water Fly Fishing’s nymph flies and dry fly collection so you’re prepared for every life stage that trout are feeding on. Don't forget to organize your small flies in a compact fly box so you can change patterns quickly when the hatch shifts.