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“A man may fish with the worm that hath eat of a king And eat of the fish that hath fed of that worm.”
William Shakespeare, Hamlet

From Fly-fishing to Aquatic Entomology
May Berenbaum

Fishing is in all probability the world’s second oldest profession. Archaeological remains reveal bones and bits of tusks fashioned into crude hooks; as technology advanced, these were replaced with copper and iron. One brilliant inspiration, hit upon by some unnamed genius as long as 3,000 years ago, was not simply to disguise the hook but to fashion it into a semblance of something delectable to attract fish. Thus were the beginnings of fly-fishing.

The first recorded artificial fly proper dates back to the Macedonians, who attached feathers to hooks to fish the Astraeus River. The historian Claudius Aelian described in great detail the imitation insects in his book De Animalium Natura (A.D.200):

Written accounts of fly-fishing are virtually nonexistent for about 1,200 years; the next appeared in 1486. Juliana Berners was the prioress of the Benedictine convent at Topwell, in the vicinity of St. Alban’s, England, where she became intimately familiar with the natural world and developed a consuming passion for insects and fishing. The result of her interest was the publication in 1486 (printed by no less than William Caxton, the man responsible for introducing the movable printing press to England) of her tome A Treatyse of Fysshynge with an Angle. The book describes in fine detail a number of flies for which the prioress provided names (some still in use today), including the dun fly, yellow may, stone fly, black louper, dun cutte, maure fly, tandy fly, wasp fly, and drake fly.

The first illustration of a fly did not appear until 1652, when John Denny depicted one in his book The Secrets of Angling. The following year was a (no pun intended) watershed year for fishing in general---it was the year that Isaak Walton published his timeless classic, The Compleat Angler. In the book, Walton described with style and enthusiasm all aspects of fishing, including the life histories of aquatic insects. He also emphasized the importance of knowing the local insect fauna and the feeding preferences of the fish. His description of the twelve kinds of artificial flies to be used on top of the water may be the first literary reference to dry fly-fishing. His book was so wildly popular that it rapidly went through several editions; the fifth edition, published in 1675, included an extensive classification of flies compiled by Charles Cotton, a Walton disciple.

The scientific revolution of the eighteenth century found its way into fly-fishing in the nineteenth century in the sense that entomology developed as a scientific discipline, and its contributions in the form of an enhanced understanding of insect ecology and life history were incorporated into the fly-fisherman’s arsenal. In England, Alfred Ronalds published The Fly-Fisher’s Entomology, in which he described flies that closely resembled real and distinctive insect species. Much of the information available today on aquatic insects was obtained as a result of career fishermen and hobbyists (by the turn of the century, sport fishing was firmly established as a national pastime). The tradition continues today; one of the finest entomological texts on aquatic insects – William McCafferty’s Aquatic Entomology – is designed for use not only by entomologists but by anglers as well.

As for actual fly-tying, there are tremendous differences of opinion and practice but basically two schools of thought exist. According to some, flies are the most effective if they are impressionistic, that is, if they capture the essence of the insect and ignore the details. Size, color, and general gestalt are the principal concerns. According to others, flies must be realistic in every detail, even down to feathering pectinate antennae or fashioning abdominal gills on mayfly larvae. All parties agree, however, that the artificial fly must look real to a fish. Obtaining the perspective of a fish is a complex mental exercise. Among other things, phenomena such as countershading and light filtering by the water column must be taken into account. An amazing assortment of materials have been drafted for use in the construction of artificial flies. Feathers are a common feature. They are particularly suitable because, in many species, banding patterns create the illusion of segmentation, a must for simulating anything insect-like. Feathers from literally dozens of species of birds have been incorporated into fly designs. Game birds in particular have been popular (perhaps because in the off-season fishermen are likely to go hunting, too). Fur or hair from a variety of mammals not only has the appropriate translucence from the fish perspective but is also buoyant and can keep a fly up on the surface of the water. Favorite furs include groundhog, lynx, badger, monkey, squirrel, bucktail, fox, and goat.

As for deciding on a design, the spectrum of choices facing an angler is not quite as broad as that facing an aquatic entomologist. Fly-tying fishermen tend to concentrate their efforts on a select few orders of aquatic insects. Of primary interest are mayflies, stoneflies, dobsonflies, and caddisflies (all of which lead lives closely tied to, if not always immersed in, water), and of secondary importance are true bugs, beetles, moths, bees, ants, and wasps (many of which are only accidentally aquatic). Despite the fact that beetles and true bugs are extremely abundant in all kinds of fresh-water habitat, they are not favored as models for flies. It’s possible that these primarily predaceous insects, equipped with potent venoms and powerful jaws, are not preferred fish food. Studies of gut contents of trout lend support to the notion that you won’t catch too many fish with a beetle (one entomologist found that less than 2% of what was in the stomach of brown trout was beetles).

The importance of intimate knowledge of insect life cycles in successful fishing is illustrated by the proliferation of detail in mayfly flies. No fewer than five types of flies represent mayflies: nymphs, duns (subimagoes or winged immatures), spinners (male and female adults), and spentwings (dead mayflies). Every year, calendars are published with recommendations on which flies to use at what time of year. Timing fly use to coincide with major insect emergences is all part of constructing the most convincing deception. Many fish display prey-switching behavior, that is, they customarily pursue selectively prey species that are most abundant. Thus a fisherman with knowledge of emergence times and population fluctuations will be able to provide fish with a more enticing lure.

Flies are classified by how they are used. Wet flies are those that are designed to sink beneath the water surface (and are popular for use with trout and salmon). They are constructed to resemble adults emerging from pupal skins at water surface, females ovipositing below the water surface, small crustaceans, or drowned surface flies. In constructing wet flies, absorbent material is used to ensure sinking, and feathers and fur are used sparingly in order to ensure room for movement. Wet flies include divided wing, closed wing, down wing (female caddisfly), hackle tip, palmer hackle (caterpillar), flat wing (female stonefly), and translucent wing (such as mayflies, with females tied so as to convey the impression of egg sacs at the tip of the abdomen, complete with wings made of fish skin).

Dry flies are designed to remain on the surface of the water. Buoyancy is key here and many floatable materials are used in their construction (e.g., cork). Of dry flies, the most popular are probably the upwing types: duns and spinners. Double-paired wings include divided wing, split wing, and hackle tip wing. Downwing types include sedges (caddisflies), alderflies, rolled wings, hair-wings and reverse wing quill. Spentwing types include dead drakes and spinners, which are recommended for quiet waters. Flatwing types are the stoneflies, and nobody knows what fanwing types like the Royal Coachman are supposed to be, but they appear to work nonetheless. There are detached body types (with the fly longer than the hook), palmer hackles (caterpillars), bivisibles (conspicuous not only to the fish but to the angler, so he or she can see where they go), parachute, and reverse fly (to simulate upstream flight). There are various nymphs depicted as well, such as the humpback (mayflies), double wingpad (stoneflies), compressed body (damsel-fly nymphs). Because these nymphs have no wings, they can’t technically speaking be considered flies (since, of course, nymphs don’t fly).

Although fly-fishing has never been unpopular, it has undergone a recent resurgence in popularity. This was evident in the success of the recent movie based on Norman Maclean’s novel, A River Runs Through It, a paean to the spiritual and restorative powers of fly-fishing. Today, devotees can order all manner of flies from a number of nationally distributed catalogues. Shirts, ties, and even jewelry featuring fly motifs and are even available to satisfy the most devoted enthusiasts.
While the habits of aquatic insects have been of intense interest to anglers for at least a millenium, they have in this century become of great importance to society at large for an entirely different reason. Because of their abundance, their diversity, and their relatively low rank in aquatic food webs, aquatic insects are particularly sensitive to changes in the quality of their habitat. Since the early 1960s, armies of entomologists, environmental engineers, and conservation biologists have been inventorying and monitoring populations of aquatic invertebrates in order to assess the environmental impact of human activities.

Of particular interest to people who assess aquatic environmental quality are the comings and goings of stoneflies and mayflies. As a rule, these insects live close to sediments and as a result are likely to come in contact with all manner of pollutants. They tend to be extremely sensitive to environmental perturbations and are susceptible to even slight increases in water temperature, acidity levels, or heavy metal contamination. A decline in the relative abundance of these insects in an aquatic community is a definite warning that the entire system has been compromised. Because mayflies and stoneflies are popular prey of game fish, a decline in their numbers is often soon followed by a decline in the diversity and abundance of the fish community.

On the other hand, chironomid midge larvae (including the bloodworms) are environmental indicators of an entirely different nature. These insects are notorious for their ability to thrive in the most horrific of environments. In one acid strip-mine lake in southern Illinois, for example, picturesquely named "Bradley’s Acid Pit," population densities of a species of midge (Chironomus near maturus) approached 50,000 per square meter, despite pH levels as low as 2.7 (on a par with vinegar). An increase in the relative abundance of chironomids in a community is usually a sign of neighborhood decline. The Environmental Protection Agency has published a list of pollution tolerances for some 230 species of chironomids, for use in water quality assessments.

Small size notwithstanding, aquatic insects may play a vital role in facilitating the recovery of aquatic ecosystems following contamination. The burrowing habits of some mayflies, for example, can accelerate the rate at which toxic materials are adsorbed into the sediment. Many herbicides, pesticides, and other organic chemical pollutants are relatively insoluble in water. Once introduced into an aquatic environment, they can either drift down into the sediment or get taken up by living organisms; of course, once buried, they pose less risk to ecosystem function than they do traveling through food chains. Generally, diffusion of these chemicals through the semisolid sediments at the bottom of a lake or river is a slow process. However, many aquatic invertebrates make their living by burrowing through these sediments. The burrowing mayfly, Hexagenia limbata, tunnels extensively underneath the sediment surface, flushing out particles that clog the burrows and pulling water through to keep themselves supplied with oxygen. This pushing and pulling has the effect of turning under surface sediment and exposing underlying sediments to dissolved materials. Overall, the quotidian activities of burrowing mayflies can more than double the rate at which water-insoluble pollutants can get adsorbed onto sediments and increase the depth at which these materials get buried.

In a sense, insects in water are like fish out of water. When the first proto-insects crawled out of the primordial muck to colonize dry land, they set in motion a process that led to the evolution of a body plan exquisitely adapted to terrestrial life. Relatively speaking, then, all freshwater insects are parvenues to freshwater environments, descended as they are from terrestrial forebears. The adjustments they have made to freshwater life are astonishingly diverse and, by all accounts successful. In a very short time (evolutionarily speaking), insects have become vital elements in the vast majority of freshwater aquatic communities.

There are limits, however, to what can be done with the basic insect body plan. Human activities have altered both the physical and biological character of freshwater environments with unprecedented speed, and may be pushing those limits to the breaking point. A food chain is only as strong as its most vulnerable link, and insects are vital links in aquatic food chains of innumerable descriptions; if we humans would like to continue to be part of freshwater aquatic communities, it behooves us to pay a little more attention to the needs of its smaller members.

Xerces board member May Berenbaum, head of the Entomology Department at the University of Illinois, is known throughout the scientific community as a gifted researcher, writer, teacher, and public speaker. She the author of Ninety-nine Gnats, Nits, and Nibblers (1989); Ninety-nine More Maggots, Mites, and Munchers (1993); and Bugs in the System (1995). She was elected to the National Academy of Sciences in 1994.

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