Frank Sawyer's Killer Bug is a great fly. Since I started tying this fly about 15 years ago it has been my most productive fly by far. What makes it even better is that it is very easy to tie and uses inexpensive materials (at least the way I tie it) just some knitting yarn, some copper wire and a Prismacolor marker.
The Grayling Killer Bug, as I believe it was originally called, was developed in the 1930s by Frank Sawyer, the same man who developed the pheasant tail nymph. At that time, Sawyer worked as a river keeper on the river Avon. As part of his duties, he was to rid the river of grayling. According to his grandson, Nick Sawyer, who runs Sawyer Nymphs in the UK, the fly that Frank developed (which imitates the gammarus pulex - what we call a scud) was more effective than netting or electro-fishing. I can believe it.
I have since seen photos of the crane fly larva, which might even be more common in our streams than scuds. It bears a striking resemblance to a Killer Bug, or rather, the Killer Bug bears a striking resemblance to crane fly larvae, and that may be what the trout are taking it for. But whatever they take it for, they do take it. I often find myself wondering, "why do I fish anything else?" Variety, I guess. Nothing I've found outperforms it.
I guess my comment above about inexpensive materials should be explained a bit, in that Sawyer tied his fly with a yarn that is no longer produced - Chadwick's 477. That yarn is now one of those almost unobtainable fly-tying materials that have achieve a near-mythical status - I would say more than polar bear hair or seal fur, more than the urine-stained fox fur for the Hendrickson (though maybe not more than the ram's scrotal hair that is, well, indispensable for the Tups Indispensable). Chadwick's 477 hasn't been produced for over 50 years now, and when the rare card is auctioned on eBay, it goes for over $100.
Sawyer is quoted as having said, "The successful attraction of this pattern is due to the fact that the particular 'darning wool' used, completely changes colour when wet." Chadwick's 477 was a fawn color, kind of a greyish brown, but it had red fibers running through it. When the yarn was wet, the red fibers gave the yarn a pinkish tan hue.
Although substitutes are sold in the UK as Killer Bug Yarn, none that I have been able to find show the pinkish-tan color when wet.
I've also read comments on various forums that suggest that any yarn will work. I'm convinced the people who say that do so only because they haven't tried one that does turn a pinkish tan (just as a lot of the people who say tenkara is just dapping or cane pole fishing have never tried it.) I think Sawyer was absolutely correct when he said the successful attraction is due to the color.
I started fishing Killer Bugs in 2008. I looked extensively for a yarn that had the "fawn" color that Sawyer described, and also had red fibers running through it to give it the pinkish hue when wet. I found none.
The yarn I settled on then (and still use today) is Jamieson's Shetland Spindrift "Sand" yarn, which is an off-white, too light even to be called "oatmeal." But it does have the red fibers running through it. To give it the requisite
tan color, I use an artist's Prismacolor marker. The color of the pen is also "Sand" -
The resulting fly,
which turns a definite pinkish tan when wet, is a very close imitation
to the scuds that have a pinkish hue. I have finally gotten a very small
sample of the original Chadwicks 477, and the Sand marker I use is just
a little too tan but the trout don't seem to care. If they don't why
should I? It seems the Prismacolor Sand color, like the Chadwicks yarn, also has been discontinued. My marker is
still usable so I have not sought out a suitable replacement.
Look for a light tan, ideally with a slight grayish hue.
The fly is tied with copper wire instead of tying thread. The copper
wire provides a little bit of extra weight, but not nearly as much as a
lead underbody or even a beadhead. (With a soft rod and a light
line, you can still tell it's a weighted fly, though.) I believe Sawyer
used a varnished copper wire that had a slightly reddish brown color. The closest match I have found is called magnet wire, but I just use the copper wire sold by fly tying shops.
Scuds can swim - fast - and for a time I fished the killer bug with quick tugs to mimic a scud's swimming action. Having fished with a truly Hi-Vis Fluorocarbon level line, and having seen strikes that I'm sure I wasn't seeing before, I now think a dead-drift approach may in fact be a better technique.
I don't know that giving action to the fly with quick tugs produces
more strikes, but it certainly causes your line to bounce around, and if
your line is bouncing around it is very hard to see the very subtle
indications of many strikes. Truly, some strikes are so subtle that they move the line much less than the motion caused by even a gentle pulsing action.
Also, when the line is bouncing, there are times that it is
slack, and a fish can spit out the fly long before you can take the
slack out of the line with your next tug.
1. Because copper wire slips pretty easily when wrapped, I start by just touching the hook shank with super glue. I find the brush applicator works better. The red colored copper wire I use with the Utah Killer Bugs isn't as slick and with it I find the super glue is not necessary.
2. Start the copper wire at the eye, trapping it just like you would with tying thread. I wrap one layer from the eye to just before the bend. The photo shows the wire starting just behind the eye, but I now start it right at the eye.
3. Start the yarn like you would start thread behind the hook eye. This photo was taken just before clipping off the tag end. Wrap to the bend, back to the eye and then back again to the bend. I try to untwist the yarn, which is two ply, so the the plies lay side by side as I am wrapping. You need to wrap tightly so the yarn doesn't start sliding around after a few fish. Some people twist the yarn more, so that it resembles a cord, which does produce a bit of a segmented look. I find the twisted yarn harder to control and have not noticed any improvement in catch rate.
4. When you get to the bend, trap the yarn with one wrap of wire, then do a five turn whip finish with the wire (four turns if you are tying on a size 14 scud hook). Tighten the wire very gently and smoothly or it will break. When it is tightened, then break off the wire tag end. Clip the yarn tag end last.
I have always done a whip finish by hand rather than with a whip finish tool. For those who prefer to use a whip finish tool, I'll pass along a tip I received from Kirk A: use a whip finish tool designed for salmon flies, which sounds like it might be larger than the standard tool.
5. While the fly is still in the vise, color it thoroughly with the Sand Prismacolor marker*. It will look brown initially, but as the color sinks in, the fly will take on a pinkish tan look, which intensifies when the fly is wet. Coloring it roughly with the marker also raises loose fibers, which create a bit of a halo effect, and gives the impression legs.
*You will have to find a substitute because Prismacolor no longer sells their Art Markers in the Sand color. Alternatively, use Jamieson's Shetland Spindrift Oyster yarn instead of Sand, which will create a Utah Killer Bug. No marker needed.
Hook: Daiichi 1560 size 12
Wire: Ultra Wire, small, copper
Yarn: Jamieson's Shetland
Marker: Prismacolor "Sand"
Hook: Daiichi 1560 size 12
Wire: Ultra Wire, small, red
Yarn: Jamieson's Shetland
Marker: Not used
The Utah Killer Bug is an adaptation made by the Tenkara Guides in Salt Lake City, UT. In an attempt to simplify the tying process, they settled on a yarn that does not require the Prismacolor marker. I now call the yarn they chose Utah Killer Bug Yarn. It is darker and quite a bit pinker than the yarn I use for the Killer Bug. When wet, both yarns darken and both show a definite pinkish tan hue. Interestingly, the Prismacolor marker I use is not completely waterproof, so after a few uses, the yarn loses much of it's brown color and bugs tied with the two yarns end up looking pretty similar.
In any event, Prismacolor has discontinued the Sand color.
I do not tie the Utah Killer bugs quite like the Tenkara Guides do - although each of the Tenkara Guides ties it a bit differently. I tie them just the same way I tie the regular Killer Bugs.
Another representation of Sawyer's Killer Bug is this watercolor by Joel
DeJong. Joel set out at the beginning of 2010 with the goal of painting
a different fly each day for the entire year and has documented his
progress in his blog A Year On The Fly. One of the flies he chose was Sawyer's Killer Bug.