What is a Mayfly

Fly fishing mayfly

In fly fishing, the mayfly is an iconic figure and probably the image most people with conjure when invisioning of the “fly” in the sport’s name. These slender aquatic insects are easily recognizable in their adult or dun form by their highly visible upright wings and long, tailed abdomens. Biologically, all mayflies undergo incomplete metamorphosis, experiencing only three major stages within their typical life cycle.

The first of these three stages is the larval stage where these bugs are commonly referred to as mayfly nymphs. The nymph stage is spent entirely beneath the surface of the water, and the type of water is entirely dependent on the particular species of mayfly. Crawlers, burrowers, clingers, and swimmers are all mayfly nymphs and all exhibit different body types and behaviors depending on their varying habitats. As the respective names make clear, crawlers crawl, burrowers burrow, clingers cling, and swimmers swim. Mayfly nymphs are most easily recognized in the field by their three long tails and gill-lined abdomens. Some are slender, some are stout, but each mayfly nymph will display these distinguishable characteristics.

From the nymph stage, the mayfly will emerge from its underwater habitat and hatch into a winged adult, subsequently living out two separate and distinct winged stages. During the first of these adult stages the mayfly is called a dun and can fly, but is not yet sexually mature and ready to propagate the species (the mayfly in its dun stage is the iconic figure of fly fishing mentioned earlier). Adult mayfly duns are notable for their dull, species-specific coloration, long and tailed abdomens, and opaque, upright wings — mayfly duns observed resting on the surface film have been compared metaphorically to tiny sailboats bobbing with the river’s current.

After sufficient time has passed (anywhere from 1 hour to a few days), the mayfly dun will undergo a final molt, shedding its outer layer to reveal a sexually mature spinner. At this point, the spinner mayfly will find and attract a mate. The females will deposit their eggs on the surface of the water and will fall to the water as a “spent spinner.” During this sexually mature life stage, mayflies take on a much richer, more vibrant coloration. Generally the spinners are dark brown, reddish, or rust colored, but many species display creams, greens, olives, and even brilliant whites in their spinner stages. Despite the wide variation in species color, all mayfly spinners are easily identified by their large transparent wings, a change from the opaque wings of the dun stage.

Mayflies are incredibly important to trout because of their wide and dense distribution throughout rivers and lakes in the world’s vast and varied temperate regions. Fy fishers have been imitating mayflies since the sport began hundreds of years ago, and having a wide selection of mayfly imitations in your fly box is never a bad idea.

Biologically speaking, a mayfly really undergoes three major stages in its typical life cycle: nymph, dun, and spinner. As far as fly fishing goes, there are five points during this life cycle that require distinct artificial fly imitations. These imitation points are: nymph, emerger, cripple, dun, and spinner. A nymph imitation is fished entirely in the subsurface and is designed to imitate the mayfly during the major portion of its larval stage. An emerger is a specific artificial fly designed to imitate a mayfly during its emergence from a nymph to a winged adult dun and is fished just beneath the water’s surface or within the surface film. A cripple is similar to an emerger, but designed to closely imitate an emergent mayfly that has been caught or trapped in the surface film by its own nymphal shuck, unable to hatch to an adult dun. The two remaining artificial flies, the dun and spinner, are designed and fished to imitate the two separate and distinct winged life stages common to all mayflies.

When packing your fly box with mayfly imitations, always consider the destination before you start filling up those little rows of slotted foam. The water type, season, local climate, and time of day will often determine which distinct hatches of mayfly species you’ll most likely encounter. Because mayflies spend the proportionally greatest time in the nymph stage, never leave for a fly fishing destination without a solid selection of mayfly nymphs and emergers on hand. Don’t underestimate the duns and spinners either. These stages in the mayfly life cycle may be short relative to the nymph stage, but they can just as easily be the ticket to an epic day on the water for a fly fisher.

When fishing a mayfly pattern, you have multiple options. However, the two most common approaches are either to fish the nymph form of the mayfly below the surface. This certainly can be done with a high stick nymphing approach, but it’s far more common for fly fishers to fish a mayfly nymph with the assistance of an indicator to better detect strikes. The second, and arguably the most enjoyable way to fly fish with a mayfly, is the dry fly technique. Here, your floating, adult mayfly pattern is presented on the surface of the water. With a natural drift (the same speed as the current) you’ll be amazed when a trout rises to take your offering. Dry fly fishing with a mayfly is the essence of the sport of fly fishing.

Take a look at the best nymph and dry fly rods we have to offer:

Leland Rod Company’s New Zealand Trout Fly Rod

Leland Rod Company’s New Zealand Dry Fly Rod