Mayflies are also called shadflies and lake flies. They are aquatic insects. They are attracted to light. They become a nuisance to people when they gather at night near doorways of homes and businesses. They sometimes gather in large numbers.Mayflies are members of the insect orderEphemeroptera. They have two pair of wings, so they are not related to houseflies or other true flies. Flies have only one pair of wings.There are many species of mayflies. They are very slender insects. Some mayflies are very small – 1/32” long. Others are longer – up to 1¼” long. The color varies, but many have dark bodies. The wings are pale. The wings may be yellow, gray, or even clear. Mayflies hold the wings together above their body when they are resting.Mayflies are aquatic insects. The females lay eggs in water. They prefer clean, fresh water. When the eggs hatch, the immature insects (nymphs) live near the bottom. They feed on organic material. Fish and other insects eat these nymphs. When the nymphs are mature, they leave the water. They spend a day or two drying off and shedding their skin. Then they fly away to mate and lay eggs.
Adult mayflies live a very short time. The males die after mating. Females die after laying their eggs. Shed skins and dried mayfly bodies dry out and crumble easily. The insect body fragments can become airborne and cause respiratory problems for some people.
Mayflies are attracted to light. They gather in large numbers around homes and commercial buildings. Making the building less attractive is the first step in controlling a mayfly problem. Porch lights can be changed from white bulbs to yellow “bug light” bulbs. Porch lights and lights attached to buildings may need to be moved away from the building. Consider reducing the light that shines from windows to avoid attracting mayflies to them at night. Insect light traps that use UV light may be helpful in attracting mayflies away from the building.