top of page

What is an Emerger Fly Pattern? An Illustrated Guide

Updated: Oct 19, 2021

Klinkhammer Emerger fly fishing pattern

Emerger fly patterns are used to imitate the time period in an aquatic insect’s life when it leaves its home on the stream bed and ascends to the surface to spread its wings and take flight as an adult. These patterns are fished on or in the surface film without added weight to the fly or leader. The materials used to tie emerger fly patterns are based upon the type of insect the angler is attempting to imitate.

In this guide we will cover:


What is an emerging aquatic insect?

An emerger isn’t technically a stage of an aquatic insect’s life cycle. It refers to an aquatic insect that's ascending up the water column to transform from its nymph or larva life cycle stage, to its subimago or adult stage.

There are two types of emerging aquatic insects that are of most importance to trout fisherman.

Mayfly Emergers

Mayflies spend the vast majority of their lives underwater. After hatching from an egg, a mayfly enters into its nymph stage. Nymphs have six legs, an exoskeleton shell, and are between 3mm and 35mm in length, depending upon species. Their early lives are spent crawling on underwater rocks and weeds to find algae and other vegetation to eat. At some point, weather conditions, barometric pressure, and other unforeseen natural forces signal to them that it’s time to move to the next stage of their lives. When this occurs, their bodies fill with air and they begin their vertical ascent toward the surface where they will become winged adults. During this ascent they struggle to escape from their exoskeleton skin and untuck their wings in preparation for taking flight once on the water’s surface.

Caddis fly Emergers

After hatching from their eggs, caddisflies enter their larva stage and appear as small grub-like worms. They have short legs located at their thorax, a tapered body that they “wiggle” to swim upside down, and range between 1 mm to 30 mm in length depending upon species. They spend their early lives crawling on steam bed rocks and “drifting” in the underwater currents. After about 30 weeks, a caddis moves into its pupa stage and dwells in a case that it builds around itself. At this point, it has developed wings that are tucked against its body, and within a few weeks it chews its way through the case to begin its ascent to the surface. During this ascent, they struggle to get to the surface where they will attempt to spread their wings away from their body and dry them off so they can take flight.


Why are Emerger Fly Patterns are Effective?

Trout quickly learn to consume more calories than they burn. Throughout their lives they see several “”opportunities” for food and learn some meals require less work than others. After struggling up the water column, emergers often become exhausted and get stuck in the surface film while trying to unfold their wings and fly away. Becoming “stuck” in the surface film and unable to swim away makes them “sitting ducks” for rising trout. (It would be like us trying to take off a waterlogged sweatshirt while at the same time trying to run away from a lion.) Emergers require less work and fewer calories burned for a trout to catch than would a fully winged moving target.

I’m not a trout dietitian, but I think we can all agree that the bigger the bug, the more calories it will provide. This is the reason some fly fisherman believe trout feed on the largest food source available to them at the time. If this were the case, maybe we should always tie on size 10 simulators?

Not exactly. Oftentimes trout prefer an emerger of a smaller insect stuck in the film over a larger one moving on the water’s surface.

Trout prefer emergers for 3 reasons:

  1. If an insect is fully emerged and moving on the water’s surface, a trout may have to expend more energy to capture its prey than it actually gains in calories from the meal.

  2. Emergers stuck in the film are exhausted and have limited fleeing capabilities. This significantly reduces the possibility a trout would “miss” its target at the time of attack.

  3. Trout see objects in the film and below the surface much better than they do above it. This clarity of vision gives them confidence in their choice of meal.


Types of Emerger Fly Patterns


Mayfly emerger patterns are designed so the body of the fly sits in or below the surface film, giving off the appearance that the insect is still struggling to break through the surface tension. Some of these patterns also include a trailing “shuck” that's designed to imitate the exoskeleton shell they are trying to break free from.


Caddis emerger patterns are also designed to drift in the surface film, but focus more on imitating movement caused by the insect trying to unfold its wings before or after reaching the surface. Many of these patterns include materials that “wiggle” in the water creating lifelike movement.


Best time to fish emerger patterns

Mayfly Emerger Fly Patterns

Mayfly emerger patterns are best fished prior to or at the beginning of a hatch. Oftentimes, anglers will spot insects in the air and fish feeding on the surface so they tie on a dry fly. While this often works, it can also cause frustrations when none of the trout seem interested. With closer examination of trout’s rise form , it becomes apparent they are in fact feeding on the species visible in the air, but not on the winged adults, and instead on the emergers stuck in the film. When trout start consistently rising, it’s often better to start with an emerger pattern instead of a traditional high riding dry fly.


Caddis Fly Emerger Fly Patterns

Caddis emerger patterns can be fished as searching/attractor patterns any time of day.

Many caddisfly species don’t create the “blanket” hatches that mayflies often do, and instead hatch sporadically. During much of the year, trout get used to seeing caddis here and there throughout the day. They’re effective patterns when no visible trout are feeding at the surface.

They're also very effective during a caddis hatch. Oftentimes anglers focus on the adults fluttering on the surface during the hatch, which can provide visual ecstasy, but they forget the insects on the surface get there by first emerging through the surface film. More often than not, there are as many trout, or more, feeding on caddis emergers in the film during a hatch than there are fish feeding on the adult insects on the surface.

A dry dropper rig can be used to fish a dry fly pattern and an emerger pattern at the same time.


How to fish emerger patterns

Emergers can be fished at different depths, but when imitating the “stuck in the film” stage, they should be fished with their bodies sitting in the surface film, while a portion of the fly is usually above the surface. The most effective presentation is a dead drift. The materials used to tie emerger patterns will often cause enough movement to get the trout's attention, but Trout key in on emergers because they are easy targets, so too much movement can signal to them that the insect isn't really “stuck”, therefore not that easy to catch.



Emerger patterns are often overlooked by anglers. Becoming stuck in the film causes them to become easy meals for hungry trout. Both mayfly and caddis fly emerger fly patterns can be fished dead drift in the surface film to imitate this vulnerable stage of the insect's life. Add a few to your fly box and increase your chances of having the fly the trout are key in on!

Noses Up!


About Us


Noses Up Fly Fishing is brought to you by two brothers and their passion for chasing wild trout on spring creeks with dry flies. We created this site to share our knowledge, catalog our adventures, and tell a few white along the way. Thanks for joining!

If you like what you see and would like to have the latest updates sent directly to your inbox, click here to sign up.

Our Top Picks

Favorite Book

Favorite Tippet

Wading Boots


Noses Up Fly Fishing is brought to you by two brothers and their passion for chasing wild trout on spring creeks with dry flies. We created this site to share our knowledge, catalog our adventures, and tell a few white along the way. Thanks for joining!

If you like what you see and would like to have the latest updates sent directly to your inbox, click here to sign up.

bottom of page