Expert Fisherman Reveals the Secret to Fishing and Tying the Perfect Light Cahill Fly

The Cahill fly pattern is one of the oldest and most well-known of the Catskill fly patterns and has been the number-one fly choice for morning and evening duns for decades.

I’m going to be straight up and honest. My experience with the Cahill pattern is minimal. For many years, I have been a massive advocate of its derivatives, the Adams pattern and various other patterns. These patterns can be as intricate as you wish to make them when at the vise, and a certain amount of respect should be shown to the tier, if you buy them.

This seemingly obvious pattern has specific body ratios and materials that make it a deadly pattern and at times, tricky to get right.

Yes, many a modern pattern may fish better or hold in the water film more naturally but there is a certain elegance about tying on a single Catskill dry and putting it out with a long cast only to watch it be gently sipped off the surface by a big brown or bow.

Guide Pro Tip: The light cahill is a pretty easy pattern to tie. I’ve got a FREE fly tying course where you can learn all the skills. Check it out with this link. 👉 How To Tie Flies (Step by Step)

Why the Light Cahill Fly is Great

To understand why the Cahill pattern is so effective, especially in the early mornings and late evenings, we need to look at what the pattern imitates and how it relates to the specific insect form.

I find this picture, Mayfly Lifecycle, the simplest way to explain it to clients and for other fly fishers to learn from. The Dun stage of the life cycle is where we need to shift our focus. This is one of the most vulnerable stages for the insect. It’s just emerged, and with its wings still drying out, it can’t do much in terms of flying away. It’s a sitting duck, so to speak, and trout tend to hone in on this free meal and feed hard!

This is the exact stage of life that was intended to be represented by Daniel Cahill back in the 1880s. A light, low-riding fly that will land as it had just emerged and drift like it is not happy.

The Cahill fly pattern is also a great pattern to learn to tie when you are starting out. It has a very basic profile, and not many materials are needed at all. As motioned earlier, it is important to get the body ratios right to ensure a successful tie. Sure, a few duds will happen, but they will still fish. In the end you will want to get this one perfect, and I know you won’t settle for anything less than par.

A Little History on the Light Cahill Fly

This is the part that I find most interesting. First invented by Daniel Cahill way back in the 1880s. Mr. Cahill was a railroad worker who had a passion for fly fishing and tying. The original Cahill pattern falls into the class of Catskill fly patterns. These are arguably some of the most famous fly patterns to have ever been tied. The Catskills are an area in the US near New York where these patterns are said to have been developed.

Many of the ideas for these thin-bodied, heavy-winged mayfly imitations are said to have been taken from the classic British chalk stream dries.

Whatever the case, these patterns fish well and are a pleasure to tie. When we look at the pattern in more depth, it was originally thought out to imitate a mayfly dun in the early even morning and evening. Whilst this technique is only really effective in the warmer months, many an angler has had great success fishing the Cahill patterns as early as September. It’s thought that the trout welcome some sort of surface action after a long cold winter of nymph and larvae eating.

What Fish Does a Light Cahill Fly Catch?

This is a trout pattern through and through. It was designed to catch trout and does so very well. With the modern advancements in the world of fly fishing and the ability to catch many different species on the fly now, the Cahill pattern could very well be used for many other surface-feeding species.

How to Setup a Light Cahill Fly

So, with the Cahill pattern being a dry fly, it needs to be fished as such. A long light leader and super light tippet are what is needed.

I fish the following: 8’6 3wt SAGE, with a WF3 floating line and a 12-foot progressive leader, finishing with a 5X- 7X tippet.

On the days that I feel a little more traditional, I will whip out my 7’ 3wt glass rod for some extra butteriness!

As I have mentioned previously, it is important to fish what you are comfortable with and have confidence in landing fish on.

What Does the Light Cahill Fly Represent

The Cahill pattern is tied to represent mayfly the dun stage of the mayfly, but it can also imitate an emerging or spent stage of the mayfly as well.

Light Cahill Fly Favorite Size and Color

As with any popular patterns, having them in a few different sizes is important. The color stays the same for this dry, it may vary slightly, but for the most part, it stays in these shades of light dun and tans.

Below is my selection of the top three patterns.

1. Classic Light Cahill– This is the original pattern in the light color format. It has been around for over a hundred years and remains one of the best patterns to fish. Fished in size #14-#18, depending on the conditions.
2. Hendrickson Light– is another one of the classics that should be in any dry fly fisher’s box. This Catskills dry style, dun grey, is a killer pattern. It =has been around for a long time and will continue to be a very popular mayfly imitation. These patterns should be fished in sizes #12 to #16
3. Bears Hi-Viz Brown Drake– This is a crawling mayfly dry fly imitation that is well worth having in your fly box. It is slightly bigger and bulkier but still a very deadly pattern to have and fish. Fished slightly bigger in size# 12 and #14 is best.

Where to Buy Light Cahill Fly

Suppose you don’t you tie your own flies, its best to support your local fly shop. They will definitely have the patterns you need if you choose to buy online use an online boutique shop that is well-known for its fly patterns.

How to Tie Light Cahill Fly

MATERIALS

• TFS 100, sizes 14-18 hook 
• Ultra 70 Tying Thread, cream
• Super-Fine Dry Fly Dubbing, light Cahill
• Lemon Wood Duck fibers
• Dry Fly Hackle, light ginger (Hackle and tail)

Get a FREE PDF of the Light Cahill Materials with a Hi-Resolution photo here 👉 Light Cahill Materials PDF

INSTRUCTION

1. Secure hook in the vise.
2. Wrap a thread body 4mm behind the hook eye.
3. Tie in the Wood Duck Feathers, facing forward.
4. Split the fibers left and right of the hook shank, creating those distinct wings.
5. Continue the thread backward, creating a balanced body taper.
6. Tie in the tail fibers a single length of the hook shank.
7. Make a dubbing noodle and wrap the thread forward 2mm behind the wing case.
8. Tie in the hackle with a concave away from you.
9. Wrap thread to just behind the hook eye.
10. Wrap the hackle forward and tie off behind the eye.
11. Whip finish and spend some time ensuring the body and wing are all in proportion.
12. This is the most important aspect of this fly pattern.

Guide Pro Tip – this pattern is very effective for skating on the surface in the evenings just before the sun is setting. Visibility is an issue, but the small surface disturbance helps both anglers and fish to see it.

One Last Cast with the Light Cahill Fly

The Cahill Fly pattern is one of those patterns that you just need to have in your fly box. Whether you are a seasoned pro or a beginner angler, this pattern works and is never far from being tied on.

I love the history and evolution of this pattern, as well as the hybrid patterns that have been tied from the Cahill fly. This is a what I love about fly fishing.

If you haven’t fished one yet, I suggest you give it a go. Besides taking you back and making you feel like you could be standing in a British chalk stream, the fly catches fish, is easy to cast, and is just an all-around pleasure to fish

Go for it!

Tight lines.

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Sources and Credit

• A big thank you to the great folks at Umpqua for picture use. World’s Best Flies