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Mayflies: What Are They and How to Get Rid of Them

Mayfly on a green leaf

Mayflies (shadflies or lake flies) are fascinating insects known for their short lifespan, often living for only a day or two. These insects, belonging to the order Ephemeroptera, are a common sight near water bodies and are recognized by their delicate, transparent wings and long, threadlike tails.

Despite their short lifespan, mayflies play a crucial role in the ecosystem. They serve as an important food source for a variety of birds, fish, and other insects. Moreover, their presence or absence can indicate the health of a water body, making them key bioindicators.

Interestingly, mayflies are also known for their unique mating process, which often results in spectacular swarms. These swarms, while a nuisance to some, are a natural spectacle that highlights the beauty and complexity of the insect world.

In this article, I’ll go through everything you need to know about mayflies, including what they are, and what they eat, as well as how to identify and get rid of them.

What is a Mayfly?

A mayfly is an insect that belongs to the order Ephemeroptera. This order, which consists of over 3,000 species worldwide, is known for its short lifespan. The term “mayfly” is somewhat misleading, as these insects can appear at any time from spring to autumn, depending on the species.

Mayfly on a green stem

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Mayflies are aquatic insects in their nymph stage, living under water for most of their life and are known for their unique life cycle.

They’re characterized by their delicate, transparent wings, which are held upright over their body when at rest. They have long, threadlike tails, usually three in number. The adults do not feed, as their primary purpose is to reproduce.

Mayflies are famous for their mass emergences, often referred to as “hatches” by fishermen. During these events, large numbers of mayflies emerge from the water, molt into their adult form, mate, and die, all within a very short period.

These hatches can be so dense that they appear on weather radar and can cause significant disruption, including slippery roads and bridges.

Despite their short adult life, mayflies play a crucial role in the ecosystem. They serve as a food source for many animals, including birds and fish. Mayfly nymphs, living in water bodies, help in breaking down decaying leaves and other organic matter, contributing to nutrient cycling in the ecosystem.

How Long Do Mayflies Live?

Mayflies are renowned for their exceptionally short life spans, a fact that has fascinated scientists and nature lovers alike. The lifespan of mayflies can be divided into two distinct stages: the nymph stage and the adult stage. Other common names for the winged stages are hadfly, sandfly, dayfly, fishfly, and drake.

The aquatic immature stage, called a nymph or naiad, is widely distributed in freshwater, although a few species can tolerate the brackish water of marine estuaries.

Mayfly larva on an aquarium

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During this stage, which can last from a few months up to a year, mayflies undergo a series of moults as they grow and develop. This stage is crucial for their survival, as it allows them to avoid predators and prepare for their brief adult life.

Once they have fully matured, mayflies transition into their adult stage, which is remarkably short. After emerging from the water, adult mayflies have a mere 24 to 72 hours to mate and lay eggs before they die. This fleeting existence has earned them the nickname “one-day insects.”

Mayfly on a green blade of grass

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It’s worth noting that the adult mayflies do not eat; their sole purpose is to reproduce. They lack functional mouths and digestive systems, further emphasizing the ephemeral nature of this stage.

In essence, while the nymph stage of a mayfly can last up to a year, their adult life is incredibly brief, often not exceeding a single day.

Lifecycle of a Mayfly

The lifecycle of a mayfly can be divided into four stages: egg, nymph, subimago, and imago or adult.

The journey begins when a female mayfly lays her eggs on the surface of a water body. Depending on the species, a single mayfly can lay anywhere from a few hundred to several thousand eggs. These eggs sink to the bottom and, within a few days to several weeks, hatch into nymphs.

Adult mayfly on water

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The nymph stage is the longest and most significant part of a mayfly’s life. The nymphs live underwater, feeding on algae, detritus, and other small organisms. They undergo a series of molts, shedding their exoskeletons as they grow. This stage can last from a few months to a couple of years, depending on the species and the environmental conditions.

Mayfly nymph on white background

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Once the nymph is fully grown, it swims to the surface of the water and molts one more time, emerging as a subimago, or dun. This is a unique stage in the mayfly’s lifecycle, not seen in any other insect group.

The subimago is an immature adult, able to fly but not yet sexually mature. It usually lasts for a few hours to a couple of days, during which the mayfly will molt one final time to become a fully mature adult, or imago.

Closeup of a mayfly nymph

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The adult stage, also known as the spinner stage, is the shortest and most fleeting. The adult mayflies are sexually mature and have only one purpose: to reproduce. They do not have functional mouths and do not eat; their entire energy reserve is devoted to reproduction.

Macro of a mayfly on a leaf

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Once they have mated and the females have laid their eggs, their purpose is fulfilled, and they die. This stage can last from a few minutes to a few days, giving rise to the mayfly’s reputation as the insect that lives for a day.

What Do Mayflies Look Like?

Mayflies are usually small to medium-sized insects, ranging in size from 0.5 to 3 cm long. They are generally pale in color, with bodies ranging from shades of yellow, brown, to olive. Some species of mayfly may even have a metallic sheen.

One of the most noticeable features of mayflies is their wings. They have two pairs of membranous wings, with the forewings being significantly larger than the hind wings. When at rest, these wings are held upright, like a pair of sails, a characteristic unique to mayflies.

Selective focus of a mayfly

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Another distinguishing feature is their elongated, thread-like bodies. The abdomen ends in two or three long, slender tail filaments, which are usually much longer than the body itself. These filaments, or “cerci,” are used for navigation and balance during flight.

Mayflies have short, flexible antennae and large compound eyes, which are particularly prominent in males. The males have larger and more developed eyes than females, which they use to spot potential mates during their short adult life.

In their nymph stage, mayflies look quite different. They are aquatic, with bodies adapted to their underwater environment. They have gills for breathing and clawed feet for clinging to rocks and vegetation.

Where Are Mayflies Found?

Mayflies are a global phenomenon and can be found in every continent except Antarctica. They are most commonly found in areas with freshwater bodies, as their lifecycle is closely tied to water.

In North America, mayflies are widespread and can be found in abundance in the regions surrounding the Great Lakes and Mississippi River due to the high availability of freshwater habitats.

They also thrive in the Northeastern United States, particularly in Pennsylvania and New York, where they are often seen in large numbers around lakes and rivers during the warmer months.

Mayfly perching on a green plant

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In Europe, mayflies are commonly found in countries like the United Kingdom, France, and Germany, especially in regions with clean, unpolluted rivers and streams.

They are also prevalent in Asian countries, particularly in Japan and China, where they are often associated with rice fields and freshwater ponds.

In Australia, mayflies are found in the eastern and southern parts of the country, particularly in New South Wales and Victoria. They are also present in the freshwater bodies of South Africa and in the river systems of South America.

Why Are They Called Mayflies?

Mayflies, also known as Ephemeropterans, have been around for hundreds of millions of years, with their fossils dating back to the Carboniferous period. The common name “mayfly” is a bit of a misnomer, and it has an interesting origin.

The name “mayfly” is derived from the fact that in many places, these insects make their most noticeable appearance in the month of May. However, it’s essential to note that their emergence is not strictly limited to this month.

Mayfly reflection

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Depending on the specific species and the climate of the region, mayflies can appear  during the summer months and often from late spring to early autumn.

In some regions, they are also known as “June bugs” or “dayflies,” which again refers to the time of their adult emergence and their short adult lifespan. The term “ephemeropteran” comes from the Greek words for “short-lived” and “wing,” further emphasizing the brevity of their adult life.

So, while the name mayfly might suggest these insects are exclusive to May, it’s more of a reference to the time of year when they are most commonly observed.

What Do Mayflies Eat?

As aquatic nymphs, Mayflies primary food source consists of algae, decaying plant matter, and microscopic organisms found in the water. Their consumption of these materials plays a significant role in the aquatic ecosystem, helping to maintain a balanced environment.

The nymphs are also known to scavenge on dead insects and other small aquatic organisms, contributing to the overall cleanliness and health of their habitat.

Mayfly on a water surface

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Once they emerge as adults, however, their diet undergoes a drastic change. In fact, adult mayflies do not eat at all. Their adult life, which can be as short as a few hours to a couple of days, is solely dedicated to reproduction.

Adult mayflies possess functionless mouthparts and digestive tracts, so they live off the energy reserves they accumulated as nymphs.

Do Mayflies Bite Or Sting?

Despite their somewhat intimidating appearance, mayflies are completely harmless to humans. They do not have the necessary physical equipment to bite or sting. Unlike mosquitoes or bees, mayflies do not have a proboscis or stinger to pierce human skin.

Mayflies belong to the order Ephemeroptera, which translates to “short-lived, winged creatures,” and their primary purpose during their brief adult life is to reproduce. They do not have developed mouths as adults because they do not eat. As a result, they also lack the capability to bite.

Mayfly on a finger

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Similarly, mayflies do not have stingers. They pose no threat to humans or pets and are not known to transmit any diseases. While their swarming behavior can be a nuisance, particularly for those living near bodies of water where mayflies are abundant, they do not cause any physical harm.

In fact, mayflies are often considered beneficial insects. They play a crucial role in the ecosystem, serving as food for a variety of species, including fish, frogs, and birds, and their presence is often an indicator of a healthy aquatic environment.

Can Mayflies Harm You?

Mayflies are generally harmless creatures. They neither bite nor sting, and they pose no direct threat to humans or pets.

However, it’s worth noting that in large numbers, mayflies can become a nuisance. They are attracted to light and can swarm around outdoor lighting fixtures, often in the thousands or even millions.

This can result in piles of dead mayflies around homes, businesses, and public areas, which need to be cleaned up promptly to prevent potential sanitation issues.

Swarm of mayflies on water surface

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In some rare cases, mayflies can cause allergic reactions in sensitive individuals. These reactions are usually mild and can include symptoms like sneezes, runny nose, or itchy eyes.

It’s important to remember that such reactions are not common and are more likely to be caused by other environmental factors.

Mayflies can also cause temporary problems for drivers. Swarms of mayflies have been known to cause accidents due to reduced visibility or slippery road conditions caused by large numbers of crushed insects on roadways.

How To Get Rid Of Mayflies

Mayflies, while harmless to humans, can be a nuisance due to their large swarms, especially during their mating season. Luckily, there are several methods you can implement to control and reduce their presence.

Lights or Zappers

Mayflies are notoriously attracted to light, which is why you often see them congregating in large numbers around street lamps, porch lights, or any other sources of artificial light. This attraction can be used to your advantage when trying to control mayfly populations.

Bug zapper hanging

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One method that is often suggested for getting rid of mayflies is using bug zappers. These devices use light to attract insects and then zap them with electricity. Bug zappers can be quite effective at killing mayflies, but they also have their drawbacks. For one, they can also kill beneficial insects that help control other pests. Plus, the zapped mayflies can leave a mess that needs to be cleaned up.

Another, more eco-friendly, option is to use lights to lure mayflies away from your home or outdoor living spaces. By placing a bright light at a distance from your house, you can draw mayflies away and reduce the number that end up in your home or buzzing around your head while you’re trying to enjoy a summer evening outdoors.

Remember though, while lights and zappers can help reduce mayfly populations, they are not a complete solution. To effectively control mayflies, it’s also important to address the source of the problem – their breeding grounds.

Manual Extermination By Sweeping Or Spraying

There are manual extermination methods you can use to control a mayfly infestation. These methods include sweeping and spraying.

Hand spraying plants

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Sweep them away: Sweeping is a simple and effective method to remove mayflies from your home or business premises. Using a broom, you can sweep the mayflies into a dustpan and then dispose of them outside. Remember to sweep gently to avoid damaging your property or causing the mayflies to disperse into other areas.

Spray them down: Another effective method is spraying. You can use a standard garden hose to spray mayflies off your walls, ceilings, and other surfaces. If you have a pressure washer, you can use this to spray a larger area more effectively. Be sure to aim the spray directly at the mayflies to dislodge them.

Sticky Traps

Another effective method to control the mayfly population in your vicinity is by using sticky traps. Sticky traps are a non-toxic and environmentally friendly solution for pest control. They work by attracting mayflies and other flying insects to their surface, where they become stuck and unable to escape.

Sticky trap hanging on a greenhouse

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Sticky traps for mayflies are usually coated with a substance that has a strong allure for these insects. The traps can be hung in areas where mayfly activity is high, such as near lights or water bodies. These traps are especially effective during the mayfly’s mating season when their numbers are at their peak.

To use sticky traps for mayflies, simply hang them in the desired location. The mayflies, drawn by the trap’s lure, will land on its sticky surface and become trapped. Over time, the trap will collect a significant number of mayflies, reducing their population in your area.

It’s important to note that while sticky traps can help control a mayfly problem, they are not a complete solution. They should be used in conjunction with other methods such as turning off lights at night and regular sweeping or spraying. Remember to replace the sticky traps regularly, especially after heavy rain.

Remove Standing Water

One of the most effective ways to control the mayfly population is to remove standing water from your property.

Standing water can be found in various places around your home or property. It could be a bird bath, a puddle that never seems to dry up, or even a bucket left out in the rain. Regardless of its source, it’s crucial to remove it as soon as possible to prevent mayflies from laying their eggs.

Stagnant water on tire

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Start by inspect the exterior of your property for any containers that could hold water. Empty them out and store them upside down so they don’t collect water in the future. If you have a bird bath or a pond, consider installing a water feature like a fountain or a waterfall. The constant movement of water will discourage mayflies from laying their eggs.

If you have areas of your lawn or garden that are prone to flooding or pooling water, consider improving your drainage. This could involve installing a French drain, or simply regrading your lawn to encourage water to flow away from your home.

Use Organic Materials

If you’re looking for a more natural way to get rid of mayflies, using organic materials like garlic or essential oils could be a good option. These methods are especially beneficial if you have pets or small children at home and want to avoid using harsh chemicals.

Garlic is a potent insect repellent due to its strong smell which many pests find off-putting. To use garlic as a deterrent, you can make a spray by blending two garlic bulbs with a small amount of water.

Cloves of garlic in a bowl

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Strain the mixture and add more water to dilute it. Spray this solution around areas where you’ve seen mayflies. The strong scent of garlic will help deter them.

Essential oils, particularly those with strong scents, can also be effective in repelling mayflies. Oils such as peppermint, citronella, eucalypts, and lavender are known to be effective against a range of pests. Mix a few drops of your chosen essential oil with water and spray it around your home. Not only will this help to repel mayflies, but it will also leave your home smelling fresh and clean.

Prevent Indoor Light From Attracting Them

Mayflies, like many other insects, are attracted to light. This can lead to swarms of them gathering around your windows and doors, and potentially entering your home. Preventive measures can be taken to minimize this indoor attraction.

Consider the type of lighting you use. Sodium vapor lights, yellow bug lights, or LED lights that emit warm colors such as yellow or orange are less attractive to mayflies than traditional incandescent, fluorescent, or mercury vapor lights. Replacing your outdoor lighting with these less attractive options can significantly reduce the number of mayflies drawn to your home.

Lamp with orange light

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Also, try to limit the amount of light that escapes from your home. This can be achieved by using blinds, shades, or curtains, especially during the hours of dusk and dawn when mayflies are most active. If possible, turn off unnecessary lights during these times to further reduce the attraction.

Plus, if you have a porch or other outdoor area with lights, consider installing motion sensor lights. These only turn on when movement is detected and will not attract mayflies when not in use.

Attract Natural Predators

One of the most environmentally friendly and sustainable ways to control the population of mayflies is by attracting their natural predators. This method involves creating an environment that is conducive for the predators, which in turn helps to keep the mayfly population in check.

Birds, bats, dragonflies, and certain species of fish and reptiles are known to feed on mayflies. By providing these creatures with suitable habitats, you can encourage them to stay in your area and help control the mayfly population.

Birds on a bird feeder

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For birds, consider installing birdhouses or bird feeders in your yard. These will attract a variety of bird species that feed on mayflies. Similarly, bat houses can be installed to attract bats, another significant predator of mayflies.

For fish, if you have a pond or a body of water nearby, you can introduce fish species that feed on mayflies. These include trout, bass, and bluegill. However, remember to check with local wildlife authorities before introducing any new species into a body of water to ensure it won’t disrupt the existing ecosystem.

Attractant plants can also be used to lure these predators. For example, plants that produce berries can attract birds, while night-blooming flowers can attract bats.

This method of pest control, known as biological control, is not only effective but also contributes to biodiversity.

However, it’s important to remember that attracting natural predators is a long-term solution and might not provide immediate relief from a mayfly infestation.

Chemical Control

If the infestation of mayflies becomes too overwhelming to handle with manual extermination or natural predators, chemical control may be necessary. However, it’s important to note that chemical control should be considered as a last resort due to potential environmental implications.

Mayflies on water

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Chemical control involves the use of pesticides, specifically designed to control mayfly populations. Some of the most commonly used chemicals include permethrin, pyrethrin, and malathion. These are usually applied as a spray and can be effective in killing mayflies at different stages of their lifecycle.

When applying these chemicals, it’s crucial to follow the manufacturer’s instructions to ensure safety and effectiveness. Protective clothing should be worn, and care should be taken to avoid contamination of water sources, as many pesticides can be harmful to aquatic life.

In some cases, professional pest control services may be required. These experts have the knowledge and experience to handle the situation safely and effectively, using the most appropriate chemical control methods.

Professional Pest Control Companies

When dealing with a mayfly infestation, it can often be beneficial to call upon the services of professional pest control companies. These companies have the experience, knowledge, and tools necessary to effectively handle and eliminate mayfly populations.

Professional pest control companies are well-versed in the habits and life cycle of mayflies. They understand that mayflies are attracted to light and that their swarming behavior can be disruptive and annoying.

Professional pest control worker with chemical spray

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These professionals also recognize that while mayflies do not bite, sting, or harm humans directly, their presence in large numbers can lead to discomfort and potential health risks.

Pest control professionals can provide a range of services to help manage a mayfly infestation. These can include the use of lights or zappers, manual extermination by sweeping or spraying, the use of sticky traps, attracting natural predators, and chemical control.

One key advantage of using a professional pest control company is their ability to apply chemical control methods safely and effectively. These methods, which often involve the use of pesticides, can be dangerous if not used correctly.

Professionals are trained in the appropriate use of these chemicals and can ensure they are applied in a way that minimizes risk to humans and pets.

Plus, pest control companies can provide advice and guidance on preventative measures to reduce the chances of a future mayfly infestation. This can include recommendations on outdoor lighting, property maintenance, and the creation of environments that attract natural predators of mayflies.

Frequently Asked Questions

Why are mayflies attracted to light?

Mayflies, like many other insects, are drawn to light. This is known as phototaxis. The exact reason for this attraction is not entirely understood, but it’s believed that they use natural light sources, such as the moon and stars, for navigation and that artificial lights confuse them.

What time of year do mayflies hatch?

Mayflies have a very particular life cycle. They spend the majority of their life underwater in their nymph stage. The adult stage is very short, often lasting just a few hours to a couple of days. The exact timing of their emergence as adults can vary depending on the species and location, but it often occurs in the spring or early summer.

  1. Are mayflies harmful to humans?

Mayflies do not bite, sting, or transmit diseases, so they are not harmful to humans in a direct sense. However, their large swarms can be a nuisance and even dangerous if they cause visibility issues for drivers.

  1. Are mayflies beneficial?

Yes, mayflies are an important part of the ecosystem. They serve as a food source for many animals, including birds and fish. Additionally, their presence is often a sign of a healthy aquatic environment as they are sensitive to pollution and other environmental disturbances.


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