What Is a Midge, and Why Trout Key On Them
“Midge” is a catch-all term for small, two-winged insects in the order Diptera, but for trout anglers the family that matters most is Chironomidae — non-biting midges. They’re not mosquitoes, despite the resemblance, and most species spend their larval stage in the water, which is exactly what makes them so important to imitate.
Midges go through complete metamorphosis: egg, larva, pupa, adult. In warm summer water that cycle can take as little as two to three weeks; in cold fall and winter water it can stretch to seven. That constant reproduction makes midges one of the most dependable year-round food sources in a trout’s diet, and often the dominant one on tailwaters, where consistent temperatures keep them hatching even in the dead of winter. Mature larvae, which turn pink to bright red from hemoglobin in their bodies, are commonly called bloodworms and are themselves a recognizable food source.
Midges also tend to dominate on heavily pressured water. As catch-and-release fishing has made trout more selective, tiny, sparse midge patterns on light tippet often out-produce larger, more obvious flies — which is exactly why it’s worth learning to fish them well rather than avoiding them.
How Small Is “Midge Small”? Reading Hook Sizes
Most anglers consider a size 18 hook the entry point into midge territory, with size 20 and smaller firmly in midge range. Some anglers fish as small as size 28 to 32. A practical way to think about it: a midge is any fly small enough that it requires a different skill set to fish, mainly because of its reduced hook gap. That smaller gap means a higher chance of missing a hook set or losing a hooked fish, which is part of why midge fishing has its own set of tactics.
Gear Adjustments for Fishing Tiny Flies
Tippet selection
Small flies fish best on light tippet — commonly 7X to 8X, in an 18- to 24-inch section at the end of the leader. On faster water you can sometimes get away with 5X to 6X, but lighter tippet usually means fewer refusals, mostly because it reduces drag rather than because fish can see the material. Even one tippet size heavier than necessary can be the difference between a drag-free drift and a refusal, since midges are light enough that any resistance in the leader transfers directly to the fly.
Rod action
A medium-action rod is a better match for midging than a fast-action rod. It still handles nymphing with an indicator, but it protects light tippet and gives a bit more forgiveness both in casting and in setting the hook.
Timing the hook set
Small flies mean small hook gaps, so it pays to pause before setting — give the fish a moment to get the fly further into its mouth before you lift. Combined with a softer, medium-action rod, that brief hesitation translates into a meaningfully higher hookup rate. When you can’t quite pick out the fly itself on the water, focus on watching a general strike zone rather than straining to track the fly — it’s easier on the eyes over a long session and you’ll still catch the rise.
Midge Rigs That Work
Nymphing with an indicator and split shot
The standard subsurface rig is a right-angle nymphing setup with an indicator and split shot. Because midges often hatch in slow current, size your leader length close to the actual depth rather than the usual “1.5 times depth” rule used for faster water. Position the shot roughly 8 inches above the fly so the nymph drifts just ahead of the weight.
Dry-dropper
Midge larva and pupa patterns are light enough to hang beneath a smaller dry fly than you’d need for a heavier, beaded nymph — even a tungsten Zebra Midge can ride under something like a size 14 Elk Hair Caddis. This combination is especially useful in low, clear water where fish are spooky of larger strike indicators, or where fish are too easily spooked for tight-line nymphing.
Midge as a dropper in a tandem nymph rig
Dropping a midge off the bend of a larger point fly — a bigger nymph or attractor — is an easy way to fish midges without needing to add extra weight to the midge itself. Larva patterns fish best near the bottom in this position; a pupa pattern with a thorax, fished in the tag position on a Euro-style rig, works well higher in the water column where it can imitate an emerging insect.
Tandem dry rigs (and why they’re a last resort)
Fishing two dry flies at once — a larger “indicator” dry with a trailing midge dry — is a common recommendation, but it comes with a real cost: two flies on the water doubles your drag, and getting even one fly drag-free is hard enough. It tends to work best on stillwater or very slow-moving water where current isn’t fighting the rig.
Reading the Hatch: Larva, Pupa, or Adult?
Because midges move through four life stages, trout frequently key on just one at a time. Early in a hatch, or when nothing is actively emerging, start with a larva pattern fished near the bottom. As the hatch builds and insects begin rising through the water column, switch to a pupa pattern, often fished higher as the top or tag fly in a tandem rig. Once fish are visibly rising, move to dry flies and emergers that sit in or just under the surface film.
Go-To Midge Patterns
Keep midge patterns sparse — two or three materials is usually plenty. Overdressed midge patterns lose the slim profile that makes them effective.
Subsurface: larva and pupa
- Zebra Midge — a simple thread body with wire ribbing; tie in black (the most consistent producer), olive, red, and purple, mainly in sizes 20-22.
- Disco Midge — a flashy pupa/emerger pattern with a tinsel body and peacock herl thorax, sizes 18-22, fished higher in the column as an emerging midge.
- Jujubee Midge — a two-tone, flash-heavy Charlie Craven pattern in sizes 18-22.
- WD-40 Emerger — versatile enough to fish on the surface or subsurface; especially useful as an unweighted dropper in a dry-dropper rig, sizes 16-22.
- Prince Nymph — not a true midge imitation, but effective in small sizes (18-20) for its buggy, high-contrast profile.
- Rainbow Killer — similar to a Zebra Midge with a brown thread body and pearl tinsel rib, sizes 18-22.
Surface: dry flies and emergers
- Griffith’s Gnat — a peacock herl pattern that doubles as a cluster-of-adults imitation in slightly larger sizes (16-20).
- RS2 Emerger — effective fished dry, in the film, or subsurface as a trailing fly; tie in olive, black, and gray, sizes 18-26.
- Mole Fly — a CDC-winged, beaver-dubbed emerger that rides with its body hanging below the surface film, sizes 20-22.
- Smokejumper — similar profile to the Mole Fly with a bulkier thorax and wingcase, sizes 18-24.
- Puff Daddy — a CDC pattern for very small, wispy flies down to size 24; also effective imitating midge clusters.
- Pat’s Top Secret Midge — a two-tone emerger effective both dry and as a nymph, sizes 20-22.
Where and When to Fish Midges
Midges hatch reliably in slow current, which makes slow seams, tailouts, and deep pockets behind structure the most consistent water to target. On bigger rivers, a stripping basket lets you manage long drifts without constantly handling the reel. Cast slightly upstream to give the rig time to sink, then high-stick the indicator as it passes before paying out line smoothly to extend the drift.
Winter is prime midge season, especially on tailwaters where stable water temperatures keep midges hatching even when every other insect has shut down. The approach doesn’t change dramatically from summer — the same tackle adjustments and rigs apply — but expect fish to hold in slower, more sheltered water as temperatures drop. If midge fishing isn’t producing and you want a change of pace with bigger, more active flies, our guide to fishing streamers covers the opposite approach.
A Simple Starter Midge Box
For a beginner building a midge-specific fly box, a compact, workable starting point is:
- Zebra Midge in black and red, sizes 18-20
- Disco Midge, size 20
- WD-40 Emerger, sizes 18-20
- RS2 Emerger in olive and gray, size 18
- Griffith’s Gnat, size 18
That short list covers the larva, pupa, and adult stages, in both subsurface and surface presentations, and is enough to fish most midge situations before you start expanding into more specialized patterns.