Mayflies (Order Ephemeroptera) are ancient insects whose sudden, synchronized emergence from water bodies can cause a temporary nuisance for nearby homes and businesses. While their presence indicates clean, unpolluted aquatic environments, the volume of their swarming events necessitates management. Adult mayflies live only for hours or a few days, dedicating their short lifespan to reproduction before they die and leave behind decaying matter. This article focuses on natural, non-chemical strategies to deter, remove, and clean up mayflies from your property.
Understanding the Attraction Factors
Mayfly populations begin their lives as aquatic nymphs, living on the bottom of freshwater streams, rivers, or lakes for up to two years. This long developmental stage ends when they emerge as winged adults, often in a mass event known as a hatch or swarm. The adults lack functional mouthparts, meaning they cannot feed, and their sole directive is to mate and lay eggs.
The primary reason adult mayflies deviate from their water source to swarm around residential areas is their attraction to artificial light sources. This phenomenon is known as positive phototaxis, where the insects are drawn toward light, especially at night. Mayflies are sensitive to short-wavelength light, including the blue and ultraviolet (UV) spectrum emitted by common outdoor fixtures, such as mercury vapor lamps and cool-white LED bulbs.
The insects’ visual system interprets these bright, high-UV light sources, drawing them away from the dimmer, natural light cues over the water. Female mayflies are also susceptible to polarized light pollution that mimics light reflecting off water, leading them to mistakenly lay eggs on surfaces like asphalt or building materials. This dual attraction creates an ecological trap, resulting in large congregations of insects near properties.
Modifying Your Property for Deterrence
Preventing mayflies from congregating on your property begins with a strategic modification of your exterior lighting. Switching out high-attraction, short-wavelength bulbs for low-attraction alternatives is the most effective preventative measure. Yellow incandescent “bug lights,” amber-toned LEDs, or high-pressure sodium vapor lamps emit light with a longer wavelength, which is less visible and appealing to mayflies.
For the duration of the swarming season, which typically occurs from spring to autumn, it is beneficial to turn off all non-essential exterior lights. If lighting is required for safety, consider installing motion-sensor fixtures that only activate when necessary, minimizing the continuous light source that draws in swarms. Closing blinds and curtains indoors also helps, as light spilling from windows can attract the insects to the exterior walls of the home.
Physical barriers can also provide an effective layer of defense against mayfly entry. Ensure that all windows and doors are fitted with fine mesh screens and that the seals around entry points are intact. Mayflies are weak fliers, and strategically placed fans on porches or near doorways can create an effective air current barrier. The strong, targeted breeze from a fan makes it difficult for the insects to fly or land, pushing them away from the immediate area.
Reducing small sources of standing water near the home can diminish local breeding sites, although major populations originate from large bodies of water. Regularly emptying items like bird baths, old tires, or buckets prevents mayfly nymphs from developing in localized areas. While major water sources are outside of homeowner control, managing these small, stagnant puddles eliminates localized attraction.
Physical Strategies for Removal and Cleanup
Once a swarm has congregated, physical removal is necessary without resorting to chemicals. For mayflies that have landed on exterior surfaces like siding, decks, or driveways, a strong jet of water can be used for effective cleanup. Hosing down the area washes the living or dead insects into the lawn or storm drains, immediately clearing the accumulated biomass.
For large accumulations of dead mayflies on sidewalks or patios, a broom and dustpan is an efficient, non-toxic method of removal. These insects dry out and crumble quickly, making sweeping a straightforward process. Indoors or on delicate outdoor furniture, a household vacuum cleaner or a shop vacuum can quickly remove the insects without causing damage.
The removed mayflies should be disposed of in a way that returns their organic matter to the ecosystem naturally. Instead of bagging them for trash collection, the collected insects can be added to a compost pile. They serve as a natural fertilizer, providing nutrients to the soil.
Alternatively, the insects can be left on the lawn or garden beds, where they will naturally decompose and serve as food for local wildlife, such as birds, fish, and spiders. This avoids the introduction of any chemical agents to the environment.