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Nymph Flies – What Are They?

You may have heard the term “Nymphing” or nymphs, but what exactly does this mean?

Nymphs are insects that live underwater before they hatch into adults. There are many forms of nymphs, because there are many insects that live in river systems (lakes as well). For trout, nymphs are an easy meal because they get dislodged from rocks and drift downstream. Trout don’t have to move far to eat nymphs, so they make up a huge part of a trouts diet.

It is much easier for a trout to eat a nymph than an adult dry fly. Less energy is needed, and trout prefer to eat nymphs most of the time. This is why “Nymphing” sub-surface flies is so effective in fly fishing. You are simply imitating what the trout are eating anyways.

This article will cover the types of nymphs most commonly found in trout streams. Different regions have different sets of bugs, but there is lots of overlap between different states and even different countries.

Mayfly Nymphs

Mayflies are probably the most important trout insect, because there’s just so many of them. Blue Winged Olives, Pale Morning Duns, Red Quills, Tricos, Green Drakes, Grey Drakes, Etc. With there being so many types of mayflies, they make up a huge part of a trouts diet.

Blue Winged Olives hatch in the shoulder seasons (Spring and Fall), while Pale Morning Duns and Drakes are more active during the warm summer months. Drakes in Colorado start to really hatch at the end of June. Tricos will start hatching in July and go into the fall months. Red Quills will hatch starting in June and will go into the fall. There are also dozens of other mayflies that are native to different areas. The list goes on and on.

As you may have guessed, mayfly nymphs are very important because they are available to trout most of the time. You would be hard pressed to find a trout stream without mayfly nymphs.

There are hundreds of mayfly nymphs patterns available at fly shops. The Rs2’s pictured above are extremely popular here in Colorado. Having an array of Rs2 colors will keep you covered for most situations on the river.

Some other popular mayfly patterns are Barr’s Emergers, Juju Baetis, and Pheasant Tails. Head into your local fly shop to get the best mayfly nymphs for your specific area.

Since mayfly nymphs are abundant, it is nice to have a fly box dedicated to them. By building out a mayfly nymph box, you can be much better prepared for fishing trout streams. It is good to have weighted and unweighted mayfly nymphs, depending on water depth and specific hatch situations. If there’s an active hatch going on, I like an unweighted mayfly nymph right near the surface. For other times, I tend to sink the nymphs deeper.

Stonefly Nymphs

Stoneflies are a very abundant insect that are available to trout for most of the year. In nymph form, they offer a larger, easy meal to trout. The Pat’s Rubber Legs pictured above is the most widely used stonefly nymph – chenille, rubber legs, and lead wire. It will fool trout on just about any river or stream.

Summer stoneflies are much larger than winter stones. In the summer, we are often fishing stonefly nymphs in sizes #6, #8, and #10. During the winter months, fishing smaller stonefly nymphs will be much more productive. “Micro stones” in sizes #14, #16 and #18 will work a lot better in the colder months.

Stoneflies have to crawl to the rivers edge before they hatch, so they are always hanging out on rocks and other debris. A lot of times, they will become dislodged and drift downstream. This is when trout really chow down on stonefly nymphs.

Caddis Nymphs

Caddis are a very important trout insect that hatch in many rivers. They start to hatch in the spring (April in Colorado), they will remain active through the summer and into the fall.

There are many types of caddis nymphs for fly fishers to use. Some caddis build cases out of rocks and debris, while others do not. With all of the different caddis nymph variations, there are many fly patterns that anglers can use.

Olive is my go-to color for caddis patterns, as most caddis nymphs are some hue of olive. I also like soft hackle on caddis nymphs, since it makes them look like an emerging insect with lots of movement. The Le Bug pictured above is a great example of this, and I will fish it whenever the caddis are active.

Midge Nymphs

Midge nymphs are pretty simple – usually thread and wire are the two main materials. Patterns like the Zebra Midge are very easy to tie, but they are extremely effective for winter fishing.

When there is a winter midge hatch, trout go bonkers for the midge adults on the surface. During these times, you will see lots of midges crawling in the snow – they look like mosquitoes.

If midges are not actively hatching, go ahead and fish some nymphs. I will fish midge nymphs in sizes #16-#26. For pressured tailwaters or crowded rivers, smaller midges work a lot better. I am usually running 6x tippet also, because the water is low and clear.

Attractor Nymphs

These are nymphs that look like nothing in particular, but they can imitate many insects.

Flies like Hare’s Ears, Pheasant Tails, Rainbow Warriors, etc – These flies aren’t a specific match to an insect, but they still look buggy. Trout will eat them because they look good and appealing, but you aren’t matching a specific hatch.

When you aren’t sure what’s hatching or what the trout are eating, throw on an attractor nymph and start fishing. Fishing attractors can be really productive on many trout streams.

Nymphing Basics

There is no doubt that nymphing is the most productive way to catch trout. By using a strike indicator, 2-3 nymphs, and some split shot – you can hook into lots of trout.

The most important parts of nymphing are weight and depth

For your weight, you will add or subtract split shot based on the waters depth and speed. Some flies come weighted, while others are not. Experimenting with weight can take some practice – you should be fishing close to the bottom – without getting snagged.

For the depth of your nymph rig, you’ll adjust your strike indicator up and down your leader. I like to multiply the waters depth by 1.5x. For a 4 foot deep hole, I will have a 6 foot long rig. This “length” will be the distance from your indicator to your first fly. The speed of the current will make your nymph rig harder to sink, which is why I like to fish deeper.

Another important factor is to achieve a “dead drift”

Natural nymphs are floating down the river with the speed of the current, and your flies should too! If your flies are dragging or drifting unnaturally, trout will avoid them and you won’t get bites.

By adding slack and mending your line, you can drift your flies naturally and fool trout. Again, this takes lots of practice, but there’s a good mending video below by Rio Products.


For all fly anglers, nymphing is a great skill to have. It may not be as exciting as fishing streamers or dry flies, but it’s just as important. If you can master nymphing, you will start catching lots of trout – which will build your confidence.

Setting up a nymph rig can be hard for beginners, as there’s lots of pieces involved. However, once you set up a few, it gets much easier.

Nymphing will always be a productive way to fly fish, and beginners should practice nymphing until they become proficient.