Mayfly Primer
These insects are the foundation of fly fishing
by Clive Schaupmeyer
Adapted from The Essential Guide to Fly-Fishing by the author. With
apologies to entomologists and ultra keen fly anglers this is a brief
introduction to the bugs we most revere.
Mayflies are the foundation of fly-fishing. The purest of "pure" fly
anglers argue that you are not fly fishing unless you are casting a dry
fly upstream to rising trout during a mayfly hatch. Fine. But most of us
just appreciate them for what they are-beautiful bugs that trout eat and
we can imitate with wet and dry flies.
They have neat names like Pale Morning Dun, Hendrickson, Light Cahill
and Blue- winged Olive.
Mayflies are one of the most obvious groups of insects in trout streams
and are of immense interest to fly anglers. They occur in large numbers
and are a favored food of trout and other fish. The aquatic forms
(nymphs) and adults (duns and spinners) lend themselves well to
imitation with artificial flies. Fishing a good mayfly hatch can be pure
delight-or hard to figure out.
Mayflies belong to the order Ephemeroptera ephemero, meaning "short
lived" and ptera meaning "wings." Adults are slender, winged insects
with two or three long, thin tails. Different species range in length
from under 1/4 inch to well over 1 inch (4 mm to about 30 mm). Most
species have four wings; however, only one pair is large and obvious.
Wings of the first stage (dun) tend to be dull or darkly mottled. After
the adult mayflies have molted into the second land stage (spinner), the
wings are light and translucent. Spinner wings may be mottled.
Body colors range from pale to black with shades and mixtures of tan,
grey, cream, green and brown predominating. Bodies are often banded with
shades of colors because they are segmented. Mayfly bodies are often
lighter on the bottom than top, which can be important when selecting
the right fly.
Mayflies undergo incomplete metamorphosis, which means they miss one of
the underwater stages common to some other insects. This cycle starts
with an adult female laying eggs in water. The eggs fall to the stream
or lake bottom and soon hatch into nymphs. Depending on the species,
mayfly nymphs crawl around the bottom, cling to rocks, swim freely or
burrow into silt. Most species spend one year in the water, and all but
the burrowing nymphs are eaten by trout regularly. The nymphs are
imitated with wet flies we call nymphs.
Exactly one year (give or take) after the eggs are dropped into the
water, the nymphs swim to the surface and emerge, or hatch, as we say.
This is of great importance to trout and trout anglers. The nymphs that
have spent the last year crawling around and under rocks now have to
swim to the water's surface. During this brief trip they are vulnerable
and trout feed readily on them. At the surface, adults emerge from their
skins or shucks - more correctly known as exoskeletons - and pump fluid into
their wings. They sit on the water surface like little sailboats for
anything from a few seconds to a few minutes while their wings dry. They
can emerge, or hatch, like this by the thousands and trout love them. We
use dry flies to imitate them while they are riding down the river
drying their wings.
The adults, called duns because they are usually dull colored, then fly
to nearby bushes. After a few hours-or perhaps a day or so-the duns molt
into a second land stage and are now called spinners. The spinners mate
near or over water, and after a short incubation period the females
return to the water surface and drop their eggs, thus completing the
cycle. The females usually die on the water surface with wings splayed
apart. We call them spent spinners.
Most mayflies have one life cycle per year. However, some mayflies,
like the many species of the blue-winged olives, are reported to have
two or more life cycles per year. Blue- winged olives hatch in the
spring and again in the fall if conditions are right.
Popular dry flies that imitate mayflies include the generic but widely
effective Adams in standard and parachute styles; light-colored
patterns, like Light Cahill, Light Hendrickson or Pale Morning Dun;
Blue-winged Olive; and patterns like Dark Hendrickson, Quill Gordon or
Rusty Spinner. Other mayfly dries of regional importance include forms
of Green and Brown Drakes. Typical hook sizes for many mayfly species
range from #12 to #18; however, a few are much larger and some smaller.
Popular mayfly patterns vary from east to west as the species change.
Popular nymphs that imitate the underwater stage of mayflies include
Hare's Ear, Pheasant Tail; Zug Bug; Prince Nymph; and Blue-winged Olive
Nymph. There are subtle differences in body thickness (or at least
length-to-width ratios) between various types of mayfly nymphs. But the
general shape and pattern of the popular Hare's Ear resembles most
mayflies' distinctive carrot shape. Most mayfly nymphs can be
successfully imitated with a generic patterns (like Hare's Ears) tied in
different body colors and a few sizes.
Emerger patterns imitate mayflies as they break through the surface
film and out of their nymphal shuck. They are usually a hybrid of nymphs
and dry flies. Typically emerger patterns are a nymph with a ball of
floating material like poly yarn or foam tied near the head. The idea is
to simulate a nymph floating at the surface and starting to crawl out of
the nymphal case.
For further reading about mayflies and insects, find copies of the following
'Handbook of Hatches' - by Dave Hughes
'Mayflies' - by Malcolm Knopp and Robert Cormier
Our closing thought is attributed to
Mark Twain
" Golf is a good walk spoiled "
Bio on Our Man In Canada
Clive Schaupmeyer is an outdoor writer and
photographer. He is the author of The Essential Guide to
Fly-Fishing, a 288-page book for novice and intermediate fly
anglers. His photo of a boy fishing was judged the best outdoor
picture of 1996 published by a member of the Outdoor Writers
of Canada. He fly-fishes for trout in Alberta's foothill and
mountain streams and for pike near his home in Brooks,
Alberta.
For information on where to find, or how to get a copy of
Clive's book, Click here!
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