Matt Dickerson: Ephemeral nature
Ephemeroptera. That is the scientific name of the family of insects known more commonly as mayflies. The word is made up of two roots that come to us from Greek, through Latin. The first root is related to the modern word ephemeral. Though ephemeral has come to mean something more general, like “fleeting” or “short-lived,” in its origins it literally meant “lasting one day.”
The other root is ptera, which comes from the word for wings. This root appears in words like helicopter (a flying machine with helix wings) and pterodactyl (having winged fingers). When we put them together we get Ephemeroptera, the mayfly, “winged for a day.” Though the entire lifespan of a mayfly is actually much longer than a day, for many species of mayflies the adult life as a winged insect may range from as long as a day to as short as a few hours.
Mayflies are aquatic macroinvertebrates. Most of their lives are spent below the water surface. They hatch from eggs on the bottom of a stream, river, or lake into their nymph form. Most common mayfly species live about a year in the water as nymphs. Unlike many other insects (including terrestrial insects like butterflies as well as other aquatic insects such as mosquitos, which transition from larva to pupa before hatching into an adult) mayflies transition directly from a nymph to a winged adult. We speak of this as hatching. When it’s time, nymphs swim quickly to the surface of the water, open their wings for the first time, and fly off.
It is then that they truly become ephemeral. Adult mayflies do not eat. They don’t even have mouth parts. They have one task during their short time as winged adults, and that is to mate. After mating, the female lands back on the surface of the water, lays its fertilized eggs, and dies.
That is what mayflies have in common. In some ways, however, lumping them all together is unfair. Mayflies come in a wide variety of shapes, sizes, colors, and even lifespans. The Ephemeroptera family has many genera, and each genera may have many species. The state of Maine alone has more than 160 verified species of mayfly, and may have as many as 200. Some are crawlers or clingers, living on rocks on the streambed or riverbed. Some are burrowers, avoiding predatory fish by getting underneath the sand or silt. Some are free swimmers. Some have three tails. Some have two. Some have bodies exceeding an inch in length, and are as long as my middle finger if you count their tails. Some could fit comfortably on the fingernail of my pinky.
One year as a nymph followed by a day as an adult is a common lifespan, but some may live as long as two years in nymph form before hatching into adults and then spend a few days as adults. Some are adapted to life in a small mountain stream, some are adapted to bigger, slow moving rivers, and some to lakes. Some species can even tolerate life in a brackish estuary. Some are carnivorous, feeding on other smaller nymphs. Others feed on algae or on the detritus of decaying plants on the bottom of the river or lake.
Even the association with a particular month of the year conjured up by their name does not come close to matching the reality. There was, indeed, one particular species of mayfly (Ephemera danica) famous for hatching in the month of May, but even in colder states like Vermont one can observe hatches of mayflies of various species from late winter throughout the spring, summer, and fall. It may be their ephemeral nature combined with the exquisite delicate beauty and fragility of their lacy wings and long tails that has given mayflies a special place in our collective consciousness and imagination. That certainly explains some of my own appreciation.
But I also know that fish appreciate them also for different reasons, and therefore I have an extra bit of appreciation for the mayfly. Although there are numerous families of aquatic insects that are an important part of the food chain in general, and the diet of a trout in particular (dragonflies, damselflies, mosquitos, black flies, and midges, to name a few), there are three especially that are dear to those who pursue trout with a fly rod: mayflies, caddisflies, and stoneflies. There are varieties of these three species that emerge in regular hatches, predictable both by time of year and time of day, sometimes in large enough numbers to induce a feeding frenzy among the trout. They are also all susceptible to pollution and habitat degradation, and thus their presence in large numbers is a good indication of the health of a stream.
There are so many species within these families that I still struggle to distinguish some varieties of mayflies from stoneflies in their nymph forms when I find them on the stream bottom, but in their adult forms they are much easier to distinguish based on their wings. A stonefly has two pairs of functioning wings, and so in flight you will see four separate wings. When resting, their wings fold backward and lay flat atop their bodies. Mayflies and caddisflies have only vestigial rear wings, and so in flight they will appear to have a single pair of wings. A caddis’s wings also fold backward, but rest in more of a tent shape when not in flight. Mayflies, in contrast with the other two, cannot fold their wings back over their bodies, and so when resting their wings stand straight up on their backs, displaying that delicate lacing for which they are justifiably famous.
Because mayflies live on the stream bottom all year, trout will also feed on them all year — when the trout are lucky. If a mayfly makes a mistake and loses its grip on its rock, getting knocked into the current, it’s likely to find itself in the mouth of a fish. I’ve read that more than 90% of a trout’s diet is below the surface, feeding on these aquatic insects in their nymph forms. Still, under normal circumstances, it requires a bit of luck for a trout to get a bite of mayfly nymph.
Unless the mayflies are hatching. A hatch of mayflies is a thing of delight, both for its beauty and for the trout feeding frenzy that may come with it. First, the mayflies have to leave the relative safety of the river bottom, swim to the surface, and then for several moments they may have to rest on the surface while their wings dry enough to take off. They are very vulnerable during this entire process when they are known to anglers as “emergers.” Of course since they might fly off at any moment, trout feeding on emergers can be very aggressive, chasing them up from the river bottom to the surface, and sometimes coming completely out of the water to catch a mayfly as it goes airborne.
Later, after mating, the females — now called “spinners” — return to the surface, lay their eggs, and die. They are not going anywhere after this, and so the hungry trout don’t have to be aggressive. This part of a hatch is known as the “spinner fall.” Trout can just lightly touch their lips to the surface like a kiss and sip in the spent mayfly. The alert angler can often tell from the behavior of the trout whether they are chasing emergers or sipping spinners, and adjust both the fly pattern and presentation accordingly.
The most important adjustment may come before reaching the river, however. Sitting on my porch several days ago near the start of our unseasonable heat wave, I saw an unusually large number of mayflies landing on the outsides of our windows. There were dozens of them across our screens. I knew a hatch was on. Though I had missed the emergers, the spinner fall would come soon. The first thing I did was grab my camera and take some photos of the beautiful creatures. The second thing I did was grab my fly rod and flies and head to the river.
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