Mayfly – Identification and Treatments

Also Known As: Shadfly, fishfly, or lake fly

How to Identify:

Mayfly – There are many species of Mayfly, but they can all be identified by their two pairs of wings, a fact which sets them apart from true flies, which only have one pair. Mayflies can vary in size from 1-30 mm long, vary in color but they typically have dark bodies with pale wings. They can also be easily identified by their elongated abdomen and double “tails’ which branch off of it.


Mayflies are aquatic insects who prefer fresh water. Female mayflies lay their eggs in water, which hatch into nymphs and live near the bottom. These nymphs eat organic material such as algae or other smaller insects. However, these nymphs are susceptible to becoming food themselves as they have many natural predators. These nymphs then leave the water and turn into subimagos, the final stage before adulthood. The subimagos then molt a final time to become sexually mature adults which only live for a few days. The males die after mating and the females die after they lay their eggs.

Adult and sub-imago mayflies are attracted to light. They can become a nuisance when large numbers of them gather at lit entrances to homes and businesses at night. It is not uncommon for large swarms of mayflies to disrupt life in the places that they invade.

How to Stop Them:

To control the mayfly population outside of your home, consider reducing or moving the lighting around the entrances at night or switching from white to yellow light bulbs. Placing UV light insect traps around the outside of your home will also help attract the insects away from your doorways and kill them.

To prevent the mayflies from getting inside of your house inspect the outside for any openings that may allow them entry. Also, leave doors closed when possible and check your window screens for any damage or holes that would allow the mayflies through. If the flies are already in your home, the most effective course of action would be to call pest control specialists who can help you control your current problem and prevent any future problems.