tactics

Color in Insects

By Rick Hafele and Dave Hughes

Sure it's a blue-winged olive. But there are a lot of shades of olive. Why? And does it matter? We continue our exclusive series from the West's leading angler/entomologists.

f you look at scientific keys for identifying insects, you will notice that color is rarely used. Sometimes color patterns will be described, such as "paired spots on abdominal segments," or "thorax with a median dark stripe," etc., but actual shades of color are rarely mentioned.

The reason for this is simple. Insect colors vary too widely to be a reliable identification characteristic. Further, one person's green is another persons olive. No two people seem to see color the same way.

While slightly different colors of similar species poses a problem, different colors of the same species are even more confusing, and unfortunately not uncommon.

In my local streams, for example, the spring hatch of March browns can vary from a light brown to a burgundy depending on the stream. Many fishermen assume they are different species, but it is actually color variations of the same insect.

What Makes Them Different?

Differences in water chemistry between streams is one factor that causes color differences. Substrate is another, because nymphs tend to camouflage themselves by taking on a color similar to the substrate they live on. Thus, streams with different colored bottoms tend to have nymphs with different colors as well. The old saying about selecting your nymph pattern to match the color of the lake or stream bottom is a good one to follow.

The food insects eat can also affect their color. There are hundreds of different species of algae living in streams, and the dominant species change seasonally and vary from stream to stream, just as the insect species vary. As a result the diet of insects varies within and between streams, causing color differences.

An even more complex factor that can affect insect colors is water temperature. Mayflies reared at different temperatures have been shown to vary in color as adults, with warmer temperatures causing somewhat paler colors.

This effect of temperature may be the basis for the saying that hatches are a darker color in the spring and lighter in the fall.

Color differences also occur between the different sexes of the same species. This is very common among damselflies and dragonflies, as well as for many mayflies. These color differences can be so striking that even professional entomologists have been fooled by describing males and females as different species.

Differences Between Nymphs and Adults

How colors change from nymphs to adults or pupa to adults can be a vexing problem for fly fishers. Unfortunately, there is little connection between the color of nymphs and adults or between pupae and adults. The nymph of a green drake, for example, is dark brown or black, while the dun is definitely green.

Caddis larvae and adults also differ dramactically, as do the emerging pupae. Some fishermen assume the pupa's color is the same or similar to the adult's color. Like the green drake, there is rarely any similarity.

There are only two ways I know to accurately match the color of caddis pupae, and both require collecting them. The first and easiest method is to collect the larval cases off the bottom with mature pupae inside. By carefully opening the cases you can discover the pupa's color.

The second is to strain the stream's current during a hatch to collect the swimming pupae. Lodging a kick screen or net between some rocks or a log is the easiest way I have found to do this. After fishing for 10 or 15 minutes, retrieve the net and examine the pupae. Because fish often concentrate their feeding on the pupae, determining their color can make the difference between success and failure.

Is It Hopeless?

The above discussion has possibly convinced you that insect colors are impossible to predict, and that you should carry all your patterns in hundreds of colors or only tie your flies at streamside with the natural in hand.

While it is true that the pattern you use on one stream may not match the color of the same hatch on another stream, all is not lost. Most insects, whether they are mayflies, stoneflies, or caddis, come in three to six basic colors. While subtle differences in shades will vary, by tying patterns in these major colors you can match most insects closely enough to be successful most of the time on most of the rivers.

--Rick Hafele

Basic Fly Patterns and Colors

Nature has a set of color themes she likes to repeat in her insects. This tendency can help you in both your fly tying and in your pattern selection when you're out on the stream.

While there are times when you need precise imitation, both in form and in color, there are many other times when you just need to be close. If you make sure your fly box always has a few trusty patterns in colors favored by Nature, you can simplify your fly fishing life--and avoid a lot of frustration.

For example, you see a lot of blue-winged olives, in sizes 12 through 20, and they represent a lot of species, not just the Baetis to which we usually append the name "blue-winged olive."

You also see a preponderance of what we in the West call pale morning duns and pale evening duns; in the East they're referred to more often as "sulfurs." Again, they cover a lot of species, but can be fished for with the same fly patterns no matter where they occur and what Latin name they bear.

One pattern--Rene Harrop's Hairwing Dun--is a particular standby for me. With just two colors, olive and pale yellow, and several sizes, you can fool trout all over the West.

Like mayflies, caddis colors are variations on a few themes. For example here are about 45 species of spotted caddis (genus Hydropsyche). You'd go crazy trying to precisely imitate them all. But you need only tie a single fly, say Al Troth's famous Elk Hair Caddis, with tan wings and a tan body, and you've covered most situations you'll encounter.

The gray sedges are equally polific. They have slate wings and dark olive bodies. Tie Jim Schollmeyer's Deer Hair Caddis variation on the standard Elk Hair Caddis, and you've matched them all.

--Dave Hughes

Rick Hafele is a professional entomologist and fly fishing writer living in Gresham, Oregon. His most recent book is Nymph Fishing Rivers and Streams. Rick's good friend Dave Hughes is fly fishing's most prolific author, with over 30 books to his credit including Trout Flies. Together they are the authors of Western Mayfly Hatches.

Uploaded 11/01/1999.

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