Creature Feature: Mayday Mayfly Mayhem

April showers bring May flowers, or in this case I suppose I should say “May-Fliers”. Okay, bad joke, but nonetheless we are introducing the mayfly as this month's Creature Feature, named for the time they emerge as adults, which commonly occurs around the month of May. Despite the irk and ire they may bring to human communities situated near large water sources, mayflies play a very important role across many ecosystems. They serve as a food source for organisms such as fish, birds, and amphibians. For any anglers out there, the mayfly is an inspirational insect that can pose or model as a potential lure for fly fishing. This is only a few of the many reasons as to why mayflies should be considered friend rather than foe. Let us dive in to learn more...

Mayflies have traits that connect to some of the earliest insects on the planet! For example, these insects are unable to fold their wings towards their abdomen. Thus, their wings always appear stretched outward, similar to dragonflies and damselflies. An additional characteristic that helps identify mayflies is that they have two or three long, tail-like structures known as styli. 

Beginning their lives in the water, a mayfly will spend most of its life as an underwater nymph, usually feeding on dead and decaying plant matter. The nymphs lack some adult characteristics, such as wings, and will instead appear as a six-legged aquatic insect, with gills that run along the sides of its abdomen. As time passes, they increase in size each time they undergo a molt - the shedding of their exoskeleton. Eventually, a mayfly nymph will reach its final stage, where they acquire wings and may leave the water. However, although they appear to be mature adults, they are dull in color and are not yet fully mature enough to reproduce. In order for most mayflies to become fully mature to mate, it must molt one last time, even after achieving their physical adult form and having grown wings. This final step makes mayflies the only known type of insect to perform two molts as a winged adult. 

After their final molt, a mayfly is considered to be imago, a term used to refer to an insect that has completed their final step in metamorphosis.Once they become a fully mature adult, to say that they are on the clock to find a mate is a bit of an understatement. Depending on the species, an adult mayfly will have anywhere between a few hours to a few days to mate, depending on the 3,000 plus species of mayfly found throughout the world. Once mating and egg deposits are complete, the adults perish and the life cycle begins once again.

Resting mayfly. Source: Missouri Department of Conservation

If you spot many mayflies dancing around a water source this season, consider it a sign of good news! This is telling that they are living in a healthy wetland environment, as they are a sensitive species to pollution.

Click here to learn more about mayflies 

Submitted by Zach Mork, naturalist, April 2024