Guest Blogger: Mary S. Kuss, Life-long avid angler, licensed PA fishing guide, founder of the Delaware Valley Women’s Fly Fishing Association

Even if your knowledge of entomology is rather limited, it’s a virtual certainty that you’ve seen the adult form of the Giant Crane Fly. These are the huge, long-legged creatures that resemble a mosquito on steroids and are often seen buzzing around outdoor lights during the warm months of the year. They are, in fact, members of the order Diptera and thus related to mosquitoes, although thank heaven they do not bite!

The larvae are rather shy and retiring, and less likely to be seen by the average person. They are semi-aquatic and live in the moist soil and leaf litter along the edges of streams. If you’re an ice fisherman you may have used a bait called “spikes,” which are Giant Crane Fly larvae.

The first time I ever a Giant Crane Fly larva was at the Stroud Water Research Laboratory, along the White Clay Creek in Avondale, PA. I was there while a student at Widener University, conducting my senior research project. My study did not involve Giant Crane Fly larvae, but I found the work of the professional scientists there of great interest. One day I was wandering around the lab to see what the researchers were up to. I immediately noticed that someone had a kettle of water boiling on a hot plate. I had been schooled that it was very poor form to eat or drink in a laboratory, although I supposed that the pros might be a little less strict about this rule. But no one was making tea. One of the biologists took the kettle over to a Pyrex dish full of big, ugly looking larvae and poured the boiling water on them. I asked what the creatures were, and why they were being exposed to this treatment. I was told that Giant Crane Fly larvae were so tough that this was the best way to kill them relatively humanely. If they were sealed up in a vial of preservative, they would still be alive the next day!

Some years later, having acquired a better knowledge of what goes on in a trout stream, I was having a look at the “leaf pack” in Ridley Creek. Autumn leaves, once in the stream, soon acquire a layer of diatoms on their surface. The leaves pile up on the upstream side of rocks, and attract various nymphs and larvae known as “shredders” because they proceed to shred the leaves—not to eat the leaves themselves but rather to eat the diatoms. I would grab a handful of leaf pack and peel the leaves off one at a time, exposing the shredders. One of the largest and most common of these insects was, wait for it, the Giant Crane Fly larva.

Now I began thinking about how some of them would inevitably find their
way into “the drift” and would make a nice mouthful for a trout or other gamefish. Research in the literature revealed a few flies tied to imitate the larvae, but they seemed rather stiff and lifeless. A fly this large needed to capture more of the essence of the natural. I did have success fishing smaller crane fly larva imitations, like the Walt’s Worm. But a good imitation for a full-size Giant Crane Fly larva evaded me–until I found out about the Mop Fly.

Mop Flies are made from the soft chenille fingers of mop heads, car wash mitts, and even some slippers and toys. My first Mop Flies were tied using fingers from a supermarket mop head in fluorescent chartreuse. One of those chenille fingers are simply lashed to a hook. Sometimes a bead head is added, and the tie-down dressed with some dubbing or other material to cover it. The chartreuse Mop Fly functions basically as a Mega Green Weenie, and it worked quite well for me. It was clearly not the right color to imitate or even suggest a Giant Crane Fly larva, however. Eventually I learned that other colors of dust mops and similar products were available, but I didn’t really want to buy the material in such quantity.

When I found that Mop Chenille was available on cards, in fly-tying-friendly quantities and colors, I thought I saw a way forward. Next I had to figure out how to turn carded chenille into those wormy-looking fingers. I dissected one of the fingers from my supermarket mop head and found that they were made by simply furling the material. This is easily done with any stranded material of sufficient strength, and may be done on or off the hook.

For Mop Flies, the off-the-hook method works best. Start with a 3-inch length of Mop Chenille. Secure one end in the vise jaws and grasp the other end with hackle pliers. Using moderate tension, twist the chenille strand until it starts to furl. Fold the strand in half over a bodkin, grab the free end and hold it against the vise jaws. Withdraw the needle and allow the furl to happen. Twist the furled finger a bit to tighten it. Remove the hackle pliers, remove the finger from the vise and twist it with your fingers to tighten it a little more. Voila!

I ordered several cards of Mop Chenille, and found that the Light Dun was a good match for the Giant Crane Fly larva. Unfortunately it seems that this color has been dropped by the supplier. I’m sure that the color of the larvae can vary a bit depending on their locale, but the ones I’ve seen are best described as a sort of dirty off-white with a darker head. The Cream color seems next best to the Light Dun, and could perhaps be tinted lightly with a gray permanent marker. Here’s my pattern:

Giant Crane Fly Larva
Hook: #10 standard wet fly, or your choice
Bead: 5/32 black, brass or tungsten
Thread: Black or dark brown 3/0 Danville Monocord or equivalent
Body: Light Dun mop chenille, furled
Dubbing: 1:1 mix of dyed black rabbit and gray muskrat fur


  1. Funny, I just tied a dozen in chartreuse, using a car mit! I will order some of this carded material. Thanks!

    1. Although I’ve made good use of the chartreuse version, I haven’t yet given this one a trial. Late-fall would be the time, when the naturals are full-size and roaming around the stream shredding those leaves. We shall see if it lives up to its promise!

  2. Recently caught a 12-inch smallmouth bass on a chartreuse mop fly! I was surprised. It was a slow evening, but this catch made all the ‘fish-less’ hours worth it! 🙂

    1. Congrats on your nice catch, Nicole. Even if you only use them as a last resort, chartreuse attractor patterns are a very nice thing to have in your bag of tricks.

  3. The description of the crane fly larvae is excellent. Thank you very much. Have never given much thought to where these imitation mosquitos came from.

    But why go through the effort of furling chenille, when you can buy a mop head or wash mitt for probably about what a card of chenille goes for in a fly shop. You don’t have to use all of it, and if you just cut off a dozen or so “fingers,” you can still use it for a mop or mitt.

    I have used mop flies on trout in chartreuse, orange red, green and blue with success. I will add some off white to my repertoire.

    1. Thanks, Jim. If I were tying large numbers of these flies, buying more dust mops or car wash mitts would be a good idea–assuming I could find the color I wanted. I only tie a few Mop Flies, though. I have a room full of fly tying materials, and a few cards of chenille take up a lot less room than a collection of dust mop heads. As for stealing a few fingers then using the rest of the product for its original purpose…..let’s just say that I’m not well known for my housekeeping. I’m also too lazy to wash the car myself, and my hubby sure isn’t going to do it for me.

  4. Mary
    Thank you for the fly tying demonstration of the CK Nymph, Baby Crayfish and the Cricket, last evening
    at the Delco chapter of TU get together. You explanation of each during the event was wonderful.

    1. Thanks for the kind words, Jay, if you ever get back here to read this. I must confess I don’t keep up with comments as well as I should.

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