Order: Insecta Family: Ephemeroptera

Etymology : Ephemeroptera from the Greek ephemeron meaning short-lived and ptera = wings. Hence, a winged creature that once it matures, it has sex, and dies almost immediately after, or in the female case: has sex, lays eggs then dies.

Entomology:

Nymph: The Mayfly is an important source of a trout's diet. A large order, its many species inhabit fresh water lakes and streams. Generally, these nymphs have large

prominent heads, with a wing case on its thorax, and long tapered body (abdomen), ending with either two or three long filament-like tails. They are very sensitive to pollution and can disappear over night because of it. Some Mayfly nymphs live up to a year in streams or lakes feeding on plankton and vegetation. Mayflies have six legs and those with a large gill structure can move rapidly by undulating their abdomen. Other species with smaller gill structure move in short bursts, rest and then move again.

Sub imago : On rivers and streams, the mayfly nymph will crawl out of the water and dry on shore, shedding its exoskeleton, and emerge as the dun or sub imago. Upon emergence the mayfly “dun”, once its wings dry, will fly to nearby bushes or weeds where it will shed its outer skin once more and become the mayfly “spinner” (imago).

On lakes, the mayfly sheds its exoskeleton just below the surface, then will ‘pop' to the surface as a dun, and once its wings dry, will fly to nearby branches where it will moult again into the spinner or imago. When these duns emerge, they appear like a flotilla of tiny sailboats on the water.

The difference between dun and spinner can be noted in a change of colour from a darker to lighter shade, the colours of which vary greatly depending on species and aquatic environment. Also, the spinner's wings are clear as opposed to the dun's, which are somewhat opaque.

Imago : This is the reproductive stage of their life cycle. During this stage, mayfly males will swarm and fly in a bobbing motion. The female flies straight through these swarms allowing a male to clasp onto her and engage in a lethal consummation.  For once the two have sex, the male goes off and dies while the female releases her eggs by dipping her abdomen onto the water's surface. Once the process of procreation is complete, the female mayfly also goes off and expires without ceremony.

John Geirach describes it this way:

We seem to have a real affection for the image of a beautiful insect that only lives for a single day (more or less) and whose only mission is to make love just once. They don't even eat. Poets got off on this as symbolic of the fleeting nature of life, love, and beauty until it became a cliché and had to be dropped or turned into a joke. The last literary reference I saw to it was in an old Playboy cartoon that showed a boy mayfly saying to girl mayfly, “What do you mean, ‘not tonight'!?”

… Technically, this behaviour is called semelparity, and it is described best by David Quammen in his wonderful book Natural Acts: “An animal or plant waits a very long time to breed only once, does so with suicidal strenuosity, and then promptly dies. The act of sexual procreation proves to be ecstatically fatal, fatally ecstatic. And the rest of us are merely left to say: Wow.” (from “Sex, Death, and Fly Fishing”)

Fishing Mayfly patterns:

Mayfly spinners are perhaps the most exciting fly to fish. When the hatch is on, usually during the late morning and early evenings, large trout will abandon all caution and feed aggressively on these flies as they touch down on the surface depositing eggs or dying. Choose a suitable pattern: Blue Dun, March Brown, Grizzly Wullf, Irresistible Adams, Red Quill Spinner etc. Depending on the water you are fly fishing, the approach and technique will vary. On rivers and streams, cast at a 45-degree angle up stream and allow the fly to free-float down stream. You can feed line as you get to the end of the casting portion to prolong the drift.

On still water, fly fishing presentation is very important. Light tippets and good imitations generally mean better success. Don't flog the water with your casts, allow the fly to settle lightly on the water, let it sit, then give it a few twitches, and wait for the water to erupt. I sometimes skate the fly over the water, then let it settle, this often gets a trout's attention and distracts him from the thousands of other ‘real' mayflies.

Mayfly nymphs are also effective patterns to fish sub-surface. Either use an intermediate sinking line with relatively short leader (3-6 feet) or a floating line with a weighted nymph. Some of the more popular nymphs are the Prince, Pheasant Tail, Hare's Ear, and Hendrickson nymphs. On rivers and streams cast into the current and allow the nymph to tumble along the bottom. When it reaches the end of its drift, retrieve it slowly to imitate it crawling along the bottom. Often on the swing is when you will get most of your strikes so be ready.

On lakes, trolling a mayfly nymph or casting close to shore then stripping it close to the bottom can be effective. If trout are keying on the emerging duns, a sink tip is good to have, coupled with a slow hesitant retrieve, provides a natural effect to the rising imitation.

Check out some other popular bugs and how to imitate and fish them: