Photo submitted by: Laura Hlusko, Mercer County Master Gardener
The mayfly pictured was captured at Lake Wilhelm near the dam so you should be able to find these bugs throughout the county's many streams, lakes, ponds and reservoirs. These are small or medium sized insects with soft bodies (though you probably won't be able to catch them by hand to feel this). At rest, they hold their wings together like the mayfly in the picture or in a similar way to how damselflies rest. The six legs hold a distinct angle and seem to hold a somewhat equal spacing around the abdomen, thorax and head of the mayfly. You might notice that they have a similar look to water spiders. Probably the most pronounced feature, to my entomologist-lacking eyes, are the 2 or sometimes 3 long hairlike tails protruding from the end of the abdomen.
Now, mayflies themselves have an interesting life cycle. Males will swarm above the water in a somewhat thick colony and females will then fly into the colony to mate. The males will actually hold onto the females and mate in air. After mating, females will fly down to the surface of the water where she lays her eggs. After all this, the female will end up never flying off the waters surface and will be devoured by waiting fish either before or after her death. The male will also die, though on land. So after this ultimate sacrifice, what happens to the eggs?
The eggs will fall the bottom of the water where they attach or stick onto stones or vegetation. These eggs will remain there for a length of time anywhere from a day to weeks before hatching. After hatching, the mayflies turn into their nymph stage (which you might attribute to teenage years). The mayfly nymphs are an aquatic life stage. Unlike the pictured adults, they do not have their wings and contain gills! They spend their time, anywhere from 1-2 years, searching for food on the relative safety of the lake bed bottom. When the time is right, the nymphs will rise to the surface, molt and rest on the water's surface to allow their wings to dry. The mayflies at this point in their life are often a dull, neutral color (as the mayfly in the photo). After drying, they fly onto land where they wait in the vegetation before they molt once more and become a more colorful specimen. Adult mayflies do not eat and live for a mere few days. Their goal? To reproduce.
Now, I was very lucky to find this mayfly on vegetation right near the water's edge. But where else can you look? Check out the lights! At night, mayflies will congregate in the hue of lights located near the water's edge.
Submitted by: Laura Hlusko, Mercer County Master Gardener