The 4 Categories of Flies

Flies can be categorized in a variety of ways. Grouping by taxonomy, stage, and size are all common. Apart from these, there’s another method that can be an effective way of keeping flies in order — their purpose. There are four main categories of fly purpose: imitative patterns, search patterns, impressionistic patterns, and attractor patterns.

Each fills a niche situation on the water, and knowing the correct one for the situation will get you into fish faster. It’s a good idea to always carry a few of each type, since you never know what you’ll find when you arrive at your spot.

Here are the four categories of flies, their purpose, and a few examples of each. This isn’t an exact science, and some flies may fit multiple categories depending on the situation. Also, note the order they are listed. Often, this is the order you’ll use as you start to understand what the fish are eating.

These categories are also a good way to organize fly boxes. Check out this and other styles in 6 Ways to Organize a Fly Box.

Search Patterns

Search patterns are usually the first thing you’ll use if you have no idea what the fish are eating. These imitate a wide variety of insects and aren’t meant to look like any one thing in particular. Their purpose is to help you narrow down what’s working so you can switch to something more specific later.

Using search patterns may take longer to get a bite, since they don’t exactly mimic what’s on the menu. But, they aren’t meant to be fished all day, so don’t worry if you only catch a fish or two while using this type of fly.

A hare's ear fly stuck in foam.

While fishing a search pattern, the goal should be to roughly figure out what size, color, profile, and depth the fish are choosing. Even though they’re very vague, search patterns may clue you in that the fish are only taking small, black insects fished deep. This gives you the opportunity to switch to something more specific that meets the criteria.

Search patterns often overlap a little with impressionistic patterns. For example, a Parachute Adams can easily be fished as a search pattern to figure out if the size, color, and profile are appropriate, and can be mistaken for a variety of insect species. On the other hand, it’s most often meant to act as a mayfly, so if the fish are eating mayflies, there’s really nothing wrong with continuing to fish it as such.

Examples of Search Patterns

Parachute Adams

Parachute hare’s ear

Beadhead hare’s ear

Prince nymph

Woolly bugger

Impressionistic Patterns

Impressionistic patterns are the logical next step after fishing a search pattern, and as mentioned, can overlap with search patterns depending on the scenario. These flies mimic a smaller variety of insects more closely, but are more versatile than narrowing down to a specific bug.

Once you’ve narrowed down a few key details like size and color with a search pattern, you can switch to an impressionistic pattern to try and imitate a more specific group of insects. For example, you may switch from fishing a generic small, black pattern to fishing a small, black, mayfly pattern.

An Adams fly in a vice.

You may be able to start the day with an impressionistic fly if you already know what’s hatching. If there are caddises lifting off the water, starting with a generic caddis pattern is a great way to go.

In addition to mimicking multiple insects fairly closely, impressionistic patterns can also mimic multiple stages. One fly may be able to imitate both a dun and an emerger depending on whether it’s fished on the surface or just below.

Examples of Impressionistic Patterns

Parachute Adams

Breadcrust

Pheasant tail

Copper John

Pat’s Rubber Legs

Parachute black gnat

Imitative Patterns

Imitative patterns are much more specific than the previous two categories. These flies mimic a particular insect and stage. Use these flies when you have figured out exactly what the fish are eating.

A green drake fly sitting on a white surface.

While impressionistic patterns may switch between stages (for example, emergers and duns), imitative patterns should be fished as a single stage. Sinking an imitative spinner probably won’t work well if the fish are looking for emergers.

Starting the day with an imitative pattern usually isn’t the best technique if you don’t know what’s working, but once you narrow things down with other categories, these patterns can be deadly. If you’re using the perfect imitative pattern for the situation, you’ll catch far more fish than someone using a search pattern in the same water.

Examples of Imitative Patterns

BWO spinner

Sparkle dun PMD

Comparadun green drake

Yellow sally

Emergent sparkle pupa

Attractor Patterns

Attractor patterns are a bit of an outlier, as they don’t necessarily fall into the same logical progression as the last three. They can really be fished at any time, but I put them at the end, since they are a great “last ditch effort” if nothing else seems to be working.

A stimulator fly in a vice.

Attractor patterns are basically exactly what they sound like — something attractive. They don’t really mimic anything. Even search patterns, though vague, mimic insects roughly. Attractor patterns, on the other hand, usually include lots of color, flash, and other gaudy features. These are meant to trigger a reaction in fish, the same way you might be drawn to a bright, colorful painting even if you have no idea what it’s supposed to be.

There isn’t much point to fishing an attractor fly if you are having success with other fly categories, since they’re usually hit or miss. But, if the fish have refused everything else, surprising them with something large and obnoxious might just be enough to get one to bite, if for no other reason than being curious.

Examples of Attractor Patterns

Double humpy

Stimulator

Chernobyl ant

Royal coachman

Royal Wulff

Ashers (in a variety of nonsensical colors)

Remember, new flies are being created all the time for different purposes, and this isn’t an exact science. Knowing the four categories, however, should give you a leg up next time you’re not sure where to start.

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This is a list I made and use for my own trips, and I think any backcountry angler will find it handy.