Black Flies: Part II--The Patterns

By Jeff Morgan

Fly anglers are fortunate that black fly larvae live in swift water and almost nobody imitates them. This allows imitations to have a lessened degree of refinement. Most of the time, a simple grub-style pattern with a cream, smoky gray, or dirty yellow dubbed body and brown dubbed head will suffice.

One of my preferred patterns is as basic as a Dai Riki 135 hook, fine silver wire for ribbing, a dubbed body, and a black beadhead. No legs, no tails, no hackle; just bare bones. On waters with dense populations of small black flies, a good imitation is a simple black grub with a gold ribbing.

For larger larva imitations, I like to imitate the gills with a small tuft of white CDC. Is this necessary? I'm not sure, but it takes only a few seconds longer per fly, and it gives me more confidence. I also like to include the bulge on the rear third of the larva's abdomen. Again, it probably makes no difference but it doesn't take any more time, effort, or money to imitate it properly.

Pupae

As far as pupae go, I have tried to imitate them for a few summers now with absolutely no significant success. Besides the stray fish that probably would have smashed a Chernobyl Hopper (if I'd had the gall to drift one over its head) none seem to touch the 8 or 9 different styles I tried. Once I learned that the pupae don't come up at all, since the adults ride to the surface totally enclosed in a bubble of air, the reason for my lack of success was clear.

Adults

For the rising adults, I only use flashy materials. I'm talking sufficient flash to sear your eyes, not the subtle "flash" of a weak-ass caddis pupa pattern. You're shooting for the basic representation of a black body surrounded by a silvery or clear halo. I achieve that look with a CDC bubble. It gives the silvery/clear halo while still keeping the internal black color. When tied properly, this fly will retain the air bubble throughout the cast and retrieve, though the fly should be dried or treated with desiccant after a few casts.

If this sounds laborious, a simple oblong shiny black bead with painted red eyes can suffice. Whatever you tie, make sure it is flashy or else you might as well be fishing a Zug Bug .

Adults

The adults rise quickly thanks to that air bubble. These little silver balls shoot towards the surface, often drifting less than two or three yards before making it to the top. This means fish must react quickly. I prefer tight line nymphing with a lift to imitate the swift upward motion towards the surface.

At other times, I use a downstream presentation with a strike indicator, raising the rod tip intermittently to get the adult to shoot up towards the surface. While the "rise" imparted by the rod tip can be done from any direction, a downstream presentation is more natural and effective because the fly stays in the same current lane and doesn't accelerate when it rises.

You could use a black Humpy to imitate adults, but why do this if it is easier and faster to tie a real imitation? I like the CDC Sleepy John Estes pattern. It floats well, looks buggy, and nobody else uses it. The combination of the dubbed CDC thorax and CDC wing makes for a fine, "buzzy" surface imprint. One look at the fly from underneath and you'll be sold.

I have done best with adult black fly imitations where riffle water starts to slow at the head of a shallow run. I think this is because the ovipositing females and rising imagos are both present in the riffle area, then get washed down to these fish. Bank water (within 5 feet of the shore) is also a prime zone for these imitations, as some females crawl to the waterline and lay eggs on logs, rocks, and vegetation.

For anyone who fishes swift mountain streams, especially those prone to flooding, I would also suggest that anywhere that you would fish a hydropsychid caddis (Hydropsyche, Arctopsyche, Cheumatopsyche), black fly larvae and rising adult patterns are an absolute requirement. The adult imitations are effective searching flies everywhere, and surprisingly effective for picky fish that have seen it all.

Patterns

The key features to match are:

  1. Simple Structure: fast water + no body else fishing the fly + common food = forgiving fish
  2. Flashy rising adults: Simuliidae make rising caddis pupae look like a convention of midwest tax accountants.
  3. Fish all stages in swift waters: Don't fall into the black flies=stagnant waters mentality

Five patterns are listed below. Click on the pattern for tying instructions.

Mini Black Fly Larva
Clear Simuliid Larva
Beadhead Simuliid
Rising Black Fly
CDC Sleepy John Estes

 
For the background on black flies, see Black Flies--Part I.

Jeff Morgan has written many articles for Westfly, mostly on entomology and fly tying. He is the author of An Angler's Guide to the Oregon Cascades and Small Stream Fly Fishing.