So, you want to get rid of mayflies (also known as fishflies and shadflies). And you want to do it ASAP.
You’ve come to the right place!
This comprehensive DIY pest control guide will teach you all the best ways to get rid of mayflies naturally.
And we’ll break it down step-by-step so you can kill these pesky flies and learn how to prevent them in the future.
Consider bookmarking this page, or saving it somewhere, because it’s quite a long read. You may have to return several times during your journey to rid these annoying pests.
But by the end of it, you’ll have everything you’ll need to kill that mayfly swarm.
You can also leave a comment and ask me questions if you ever need additional help (at the end of the article). And I’ll try to get back to you ASAP.
Sound good? Let’s get rid of your fishfly problem!
Last updated: 1/21/21. Updated for accuracy and more exclusion techniques.
What’s a mayfly?
Mayflies are small flies with an elongated body with a pair of wings.
They’re most often referenced as “miniature mosquitoes” as they have a similar appearance in body shape, but not size.
These species are part of the Ephemeroptera order, which are part of the Palaeoptera division.
There are thousands of mayfly species worldwide, with over 400 genera in 42 families so far. You can read more about their classification on Wikipedia.
They do look quite similar to smaller versions of dragonflies or damselflies. They’re about 1” long and have a small pair of antennae, which is a giveaway that they’re not mosquitoes.
Mayflies also have 6 limbs, and a large, transparent pair of wings that are larger than their own body length.
The body is typically black, yellow, or other shades of dull colors. The wings are always transparent, though they may have dark linings going through them.
Mayflies also have a dual “tail” that extends from their bodies.
Mayfly vs. fishfly vs. shad fly
Mayflies, fishflies, and shad flies are all the same thing.
They’re just common names of the same pest. Typically, they’re called mayflies because they’re most often found during May.
That’s the most common season you’ll have to deal with these pests.
And when you see them, they’ll often be in huge swarms, otherwise known as mayfly swarms. You’ll find out how to deal with mayfly swarms later in this pest control guide.
Note that they don’t only come out during the month of May. they can also appear earlier or later than May, depending on what species of mayflies you’re dealing with. And environmental conditions can also make a huge difference.
Warmer weather with plenty of humidity will give birth to larger swarms of these pests, and possibly earlier than May.
Mayflies have plenty of names, but they all refer to the same pest:
- Canadian soldiers
- Up-winged flies
- March brown mayfly
They’re also often confused with dragonflies, damselflies, and other similar winged insects.
Are mayflies actually flies?
Believe it or not, mayflies aren’t flies, but they can fly.
Even though they look like giant dragonflies or crane flies, they have their own unique characteristics.
They’re actually classified as aquatic pests and they do live in water. However, when they become a pest, they’re typically out of the water and that’s when humans start to take notice.
For those with ponds, fish tanks, and swimming pools, mayflies may prove to be a problem.
They’re often traded around the United States in the pet market amongst hobbyists.
Fish, reptiles, and other pets will eat mayflies as a source of food. Because they’re so easy to breed and readily available, many people grow them in their home under controlled conditions to feed to their pets.
What does a mayfly look like?
The most distinguishing characteristic of the mayfly would be the tail. Mayfly anatomy is pretty straightforward.
They may have two or three tails that extend from their bodies as they travel around. Mayflies are aquatic species once again and can swim very quickly. As they swim, they use their tails to help them maneuver the waters.
Out of the water, they have a large pair of wings with 6 legs and dark coloration with small antennae.
Again, they range about 1” in length and have a large wingspan. You’ll often see them in shades of black with striped designs.
What’s the life cycle of a mayfly?
Mayflies have a complicated life cycle for being such a simple species. They have a total of 4 total phases they go through.
Mayflies lay eggs and start out in egg form. The eggs vary in size and color depending on the species, and the number of eggs produced can range from less than 50 to over 8,000.
An adult female mayfly will lay eggs in a water source, to which then they’ll sink and settle on the sediment bed, or stick to any surface on the way down. The eggs are sticky and range from circle, sphere, oval, and rounded.
After the eggs are laid, they’ll hatch in about 14 days. This depends on the environment, weather, temperature, and more, which can all affect how fast the egg incubates.
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There will also be periods of time where the egg will completely halt production, known as diapause. This lets them avoid hostile conditions for the nymphs developing within each egg.
This kind of evolution allows mayflies to populate quickly.
Aquatic mayfly nymph (unwinged)
After the nymphs are born, they’ll develop over the course of 24 months.
There are dozens of molts during this phase. A nymph may molt up to 50 times and once they’re done molting, the skin will split down their back. Then the wings come out.
This is the subimago form (also known as the dun). The subimago will then fly out of the water and find nearby shelter. A final molt will take place over the course of a few hours, leading to the imago stage, also known as a spinner.
Mayflies will then be in the second-to-last phase. The imago phase has visible wings that are opaque and colored with light blue, gray, or yellow pigmentation.
The veins of the mayfly are what’s noticeable within the wings, but not always. They’ll also start growing longer tails and limbs during this part of the mayfly life cycle.
Adult mayflies (winged)
These are the only species known to molt after wings have been developed.
After the final molt and the mayfly is officially an adult, mating will take place. Male and female mayflies will mate and the female will deposit her eggs, also known as oviposition.
This phase only lasts for a few hours and the female will be killed quickly in her adult life.
Female adult mayflies only have their wings for a very short period of time. Females who can hold onto their eggs for two days may perform mating dances.
Female mayflies will drop the eggs from several inches up into water sources, and others will fly close to the water’s surface and “touch” the water with her abdomen.
Other times they’ll deposit on objects that are sticking out of the water and deposit them on the underside so they’re underwater.
Of course, this makes them vulnerable to predators in the water who will eat mayflies naturally.
After the eggs are deposited from the female, the female will die shortly after. Mayflies don’t live more than a day or two in their adult lives. Some species only live for a few hours while others live for a few days at most.
But generally, mayflies have very short lifespans and are a fascinating species of study.
Mayfly mating dances
Sometimes male groups will perform a mating dance over the water near nighttime. They’ll fly into an air current and make up and down patterns. Females will then join the mayfly swarm.
This is where mating occurs. Males will approach the females from under and complete mating on the wing. Males will grasp the females using their legs to complete mating.
The mated females will then deposit her eggs as described earlier.
Do mayflies have a purpose?
Mayflies are an important part of the ecosystem.
They provide a food source for many fish and reptiles found in the wild, and since they’re so abundant, some predators rely on mayflies for a steady source of food.
Just like any other ecosystem, mayflies have their purpose to sustain and maintain any ecosystem.
Mayflies are defenseless and can only scurry away in the water or fly away in the air.
Because they’re so abundant, many predators have evolved to easily catch and eat mayflies. They’re easiest to eat when they’re in their nymph form in the water.
Since they spend most of their life aquatically, there are plenty of predators that eat them.
Frogs, newts, amphibians, birds, rodents, and even some mammals all eat mayflies. Since mayflies have both an aquatic life and an airborne life, they provide a food source for both sea and air predators who prey on mayflies.
What do mayflies eat?
Mayflies also eat various types of algae in the wild.
Their mouths are evolved to feed on various types of algae.
Aquatic nymphs will scavenge small plant pieces or algae that are living on objects like stones, rocks, and logs. Some will swim through the water and eat floating algae or algae in the water.
Adult form mayflies will also feed on various vegetable matter and continue eating algae diets above water. But they have vestigial mouthparts so they can barely eat, and probably won’t.
They can dive to the water surface and scavenge algae on various surfaces. Note that mayflies can still go underwater even as adults with a pair of wings.
Where are mayflies found in the US?
Mayflies are found all over the United States and worldwide. They’re not specific to any state and are widespread in North America.
However, they typically prefer areas with cleaner rivers and streams with warmer conditions.
Some states do have more mayfly problems compared to other states, such as Connecticut and Michigan. If you live in either of these states, mayflies can be so prevalent that there’s not much you can do to rid the swarms since they’re native to the area.
When is mayfly season in 2019? 2020?
Mayflies typically surface around the start of the warmer months, around summertime.
As the name says, you’ll often see them in May.
However, they can also surface early April or late June, depending on temperature and environmental conditions. Mayfly season for 2019 is already over, and the next mayfly season for 2020 will be in May of next year.
Do mayflies bite or sting?
No, they don’t. Mayflies actually don’t even have mouths to feed with, believe it or not.
Mayflies have vestigial mouths and don’t have any parts that would harm you by biting, stinging, or otherwise hurting your skin. It’s impossible for them to ever break human skin, so you have nothing to worry about in terms of ever getting stung or bitten by a mayfly.
How long do mayflies live?
Because of their limited mouths, their adult life is very short.
They have a much longer lifespan during their aquatic life, but once they become adults, sprout wings, and exit the water, they typically live for 24 hours. They have very poor eating mechanics as they can’t really sustain themselves as an adult.
During their aquatic life as a nymph, they have vestigial mouthparts, which means they don’t actually have a complete mouth.
They barely have a mouth as it is and rather have remnants of what a mouth they once had- probably way back in time. Or they evolved with very basic mouthparts because of their lifecycle.
Are mayflies dangerous?
Since they don’t bite, sting, nor really harbor bacteria, they’re not really that dangerous.
They’re not dangerous to humans, children, or pets unless they’re swarming.
The most risk that can stem from mayflies comes when it’s mating time for them, as they form large mayfly swarms which can pose a risk to drivers. Because of the sheer number of flies at one time, they can literally block your vision as you drive. They can also create slippery road conditions from the buildup of mayflies.
This is when they pose a real risk. But if you’re in an area where they’re simply buzzing around outdoors in huge numbers, you don’t really have much to worry about.
Mayflies will land on buildings and structures around your home, such as:
- Walls of your home
- Trailer homes
- Any other nearby structure
Should they form a swarm nearby, they’ll land on anything and everything that they possibly can. If you’ve seen thousands upon thousands of flies landing all over your property, that’s a mayfly swarm.
What to do about a mayfly swarm
You should do the following if you ever get caught in a mayfly swarm:
- Walk slowly and carefully to exit the swarm
- Hold your breath and take light inhales with your face and nose covered when you do
- Cover your face, ears, nose, and mouth as you walk through the swarm
- Squint your eyes as much as possible without risking your safety
- Do NOT attempt to smush them
If you’re driving through a mayfly swarm, consider using these safety precautions:
- Drive extremely slowly and carefully
- Turn on your headlights and high beams
- Don’t use your windshield wipers as this will squash them and make it harder to see, unless absolutely necessary
- Watch the road
- Keep an eye out for hazard/road signs
- Watch for traffic lights
- Watch for pedestrians
- Honk your horn to alert others when necessary for guidance
- Roll up all your windows
- Close your sunroof
- Don’t exit the vehicle unless necessary
- Park the car if needed
- Alert surrounding traffic
- Don’t brake abruptly
All of these safety tips should help you get through a mayfly swarm. Use at your own risk. Always exercise caution and common sense at all times.
Here’s a video demonstrating how dense these swarms can be- just from last year in 2020:
Are mayflies poisonous?
No. mayflies aren’t poisonous and they don’t sting or bite.
They’re also known to be relatively bacteria-free and don’t have any serious risk of any possible disease transfer.
Are mayflies bad to have?
It depends on who you’re asking.
If you’re asking a researcher? No. mayflies are a very good sign of environmental quality and water quality. Some researchers can tell the state of an ecosystem just by the abundance of mayflies.
However, for the typical homeowner, mayflies can definitely be a real pest. Seeing thousands of small flies landing on all your walls, patio doors, windows, doors, and garages all seemingly overnight can be a real scare.
Thankfully, mayflies will disappear on their own over time, unless you live in an area that’s just sprawling with mayflies.
Native areas will have nearly permanent mayfly problems as it’s impossible to get rid of mayflies permanently and to keep every single one away from your home.
You’d have to move to another area if that’s the case. Preferably way from lakes, ponds, and streams.
Do mayflies eat mosquitoes?
No, they don’t.
Mayflies don’t have working mouths in their adult forms, so there’s no way they can catch, kill, nor eat mosquitoes when they’re fully grown and are capable of flight.
However, in the aquatic nymph period of their lifecycle, they do scavenge for free-floating or attached plant matter. This includes algae and other small bits of plants that are stuck on logs, rocks, or the lake bed.
They could theoretically eat mosquito larvae as a nymph during this part of their life, but there’s no real scientific proof that they do. And definitely not enough evidence that mayflies are good for mosquito control.
So if you plan to use mayflies to control or eat mosquitoes, that’s probably not going to be effective.
How do you catch a mayfly?
You can catch mayflies by setting up traps. There are quite a few types of traps you can build to catch them, and here are some you may want to check out later in this guide.
How to kill mayflies
This section of the guide goes over how to kill mayflies (without using chemicals).
There are a ton of different methods to get rid of mayflies, so check them out and see what works best for you.
It’s best practice to use a combination of different traps to best get rid of them. See what works and what doesn’t.
DIY mayfly bottle trap
What you’ll need:
- 2-liter bottle
- 1 cup of water
- 1 cup of sugar
How to make the trap:
- Cut off the top part of the bottle using the scissors, where the neck starts converging to fit the cap
- Pour in the sugar
- Pour in the water
- Take the top that you cut off and turn it upside down and shove it into the bottle.
Now you should the bottle with an inverted top.
How the trap works:
- Mayflies will smell the sugar water and fly in through the funnel. As they go in to feed, they won’t be able to get back out.
How to use the trap:
- Place it anywhere where you notice mayfly activity. The trap will work automatically without you having to do anything.
- Replace as needed when the trap gets full of flies and is no longer effective. You can dispose of the trap in the trash without any cleanup required.
Glue traps/sticky traps
You can buy sticky tape or trap sat any hardware store.
Use the sticky tape as directed, and apply the tape to various surfaces such as:
- Doors frames
- Patio doors
Fly tape is cheap and effective. Cleaning it up is a pain though, so there’s definitely a tradeoff compared to using other various traps outlined in this DIY pest guide. Be sure to review the active ingredients and avoid any synthetic or dangerous compounds when you can.
Mayflies will be attracted to bug zappers at night.
These work effectively well in the middle of mayfly swarms. Larger swarms require larger zappers, so be sure you get the right size for adequate levels of protection.
Also, be sure to clean the zapper as needed because they can get clogged quickly.
Why are there so many mayflies?
If you’ve never seen a mayfly swarm, you probably don’t know how bad they can actually be.
Mayflies are highly prolific and do mating dances and swarm together during these events. The swarms can become so thick that you can’t even see through them- with thousands upon thousands of mayflies all swarming and mating together at once.
These swarms can be dangerous for drivers or pedestrians and where you should watch out.
Swarms can’t really be eliminated, nor can you do much about them. This is something that a natural approach won’t be sufficient. A professional exterminator would be required to manage a mayfly volume of this size.
How do I get rid of mayflies in my house?
You can use a combination of DIY traps, commercial traps, and even a basic fly swatter.
If you have a constant mayfly problem in your house, consider setting up traps around the home where there’s mayfly activity.
To get rid of single flies or smaller amounts, use a fly swatter.
How long does a mayfly infestation last?
Mayflies have a very short lifespan, which ranges from just a few minutes to about three days, at most.
They become a problem when they can fly after their aquatic life. And this is when people start getting annoyed by them.
Thankfully, they don’t have much time to fly around as an adult, and this makes a mayfly infestation relatively short. You may get a ton of them flying around your house and garden, but this won’t last more than a few days.
Of course, if you live in an area where mayflies are native, you may get swarm after swarm from different colonies.
Traps, poison, and other natural repellents are useful for smaller swarms or just mayflies that have found their way into your home. For larger swarms, there isn’t much that can be done without professional help.
How to keep mayflies away from your home or garden
If you want to keep mayflies away from you, you should get rid of the things that mayflies are attracted to.
Here are various things that mayflies will gravitate towards. Controlling these two factors will reduce the population that hovers around your yard or home.
Stagnant or low-flowing water
After a nymph emerges out of the water as an adult with wings, they’re going to fly around and look for a mate. Adult mayflies with such a short lifespan need to find a mate quickly and breed.
After breeding, female mayflies will look for standing or stagnant water.
A water source that’s accessible to them will be their top priority after they mate. Any lake, pond, stream, river, or anything of the sort will be sufficient for the female to deposit her eggs.
You can minimize mayflies by getting rid of any standing water near your house.
Of course, not everyone can do this. If you have a flowing river or giant lake, that’s not a possibility.
But for those with small ponds, swimming pools, or controlled bodies of water, they can definitely do something to get rid of the water source.
Consider the following to get rid of mayflies in nearby water sources:
- Cover your pool or pond
- Remove the pond
- Add natural mayfly nymph predators to the water
- Use chemicals to control pests
- Control algae and keep the pond or pool clean
- Remove leaves and debris from water sources
Mayflies, like most flying pests, are attracted to lights.
They tend to gravitate towards a brighter, natural white light. If you use strong lighting in your yard or around your home, consider getting rid of them or dimming them to reduce the number of mayflies.
Some lights to consider controlling:
- Patio lights
- Pathway lights
- Deck lights
- Shed lights
- Outdoor housing
- String lights
- Outdoor LED lights
- Table lights
Also, keep in mind:
- Any kind of lighting outdoors will attract mayflies. If you can get rid of the light source or relocate them, this may help. You can also add bug zappers next to these lights to attract the mayflies into the trap.
- Also, consider the lights within your home. Shut your blinds or turn off your lights at night when unneeded to reduce the number of pests attracted to your home.
- Be sure you replace all screens on your patio doors, windows, and other areas.
How to keep mayflies away
There are a few different ways you can repel flies naturally from you or your home and garden.
This part of the guide covers some cheap, DIY methods you can use to keep these annoying pests away from you and your home. Utilize these natural repellents and combine them for the most effective approach.
Common garlic has a strong scent and has been proven by anecdotal evidence that it’s effective in naturally repelling mayflies. Don’t use it near dogs and always do your research with any other pets.
Garlic can be bought at any grocery store for cheap. You can use garlic cloves, minced, or even whole garlic that’s been cut into any shape. The point is to release the natural odor from the garlic to repel the flies.
You can also make garlic spray by mixing water and minced garlic into a spray bottle in equal parts.
Let the mixture sit for at least 24 hours, then spray it whenever you notice mayflies to be present. You can spray this mixture around many locations and objects, such as surfaces, walls, doors, patios, decks, windows, and even directly onto small mayfly swarms.
If you notice a swarm of mayflies outdoors, you can use a water hose with an adjustable nozzle to spray them away. They’re sensitive to water, especially if the water pressure is strong. Use a “shower” setting and spray directly onto the swarm.
This also works against mayflies on your walls or home. The water will wash them down and they’ll likely drown in the pool collecting on the floor.
Removing them manually
You can get rid of mayflies with a sweeping broom en masse.
Use the broom to catch mayflies on the floor or walls and sweep them into a dust bin and then dispose of them. You can also use the broom to reach areas such as roofing for awnings on your home.
Essential oils and mayflies
Strong smelling essential oils like peppermint oil or cinnamon can both repel flies.
You can buy these oils at any grocery store and simply pour the mixture directly into a spray bottle, then spray the solution around your home where you notice mayfly activity.
Reapply the oil every week. Switch up the oil if one doesn’t work.
Some of the most popular essential oils for pests are:
- Peppermint oil
- Tea tree oil
- Cinnamon oil
- Lavender oil
- Sweet birch
- Ylang ylang
Note that some even though these oils are natural, some oils may be dangerous to pets or those who have allergies, so do your research first.
Attracting natural mayfly predators
Mayflies have a ton of natural predators that’ll eat them up without hesitation.
Depending on what part of the mayflies life cycle you’re trying to stop, you can attract a few predators to help you out. Look for ones that are native to your specific area for easier baiting.
During the aquatic nymph period, you can attract these predators to eat mayflies:
- Water beetles
- Various other amphibians
When mayflies get wings and are found on land, you can utilize these predators:
- Predatory beetles
- Most reptiles
- Most bird species
As mentioned previously, mayflies only live for a few days in the adult form that can fly.
They’ll all disappear suddenly if you just wait a day or two. Of course, there will be a lot to clean up if they all get killed on your property, but this approach needs no work and is the most natural.
But if you live in an area where swarm after swarm of mayflies come, you’ll have to consider hiring a professional or using commercial poisons. Because there are so many, you may just have to wait it out until mayfly season ends.
Sometimes the natural solution doesn’t work and you need a stronger approach.
These are the most common ways you can get rid of them, however, do your research first as they can definitely be harmful to humans and the environment (and your pets).
Commercial mayfly killer
Sometimes, natural approaches may not be enough. Mayflies are often found in the thousands, so you may have to use more aggressive approaches to rid them for good.
You can use a variety of fly killer sprays and apply as directed.
These are effective in killing mayflies for people who live next to a lake or area native to fly populations. There are a ton of them that you can buy at any hardware store. Do your research and read reviews. Use something with organic or natural components as a first resort.
Chemical foggers are powerful and can take down large colonies of mayflies, however, they do cause other damage to the ecosystem around you and can also be dangerous to your own health (and your pets and kids).
So always consult with a professional before using chemical pesticides. There are also some laws that protect against mayflies, as they’re an important “checker” to measure water quality and health of the ecosystem.
Using foggers can kill them en masse, which may be illegal in some states. Other states may prohibit harming them at all. Be sure to consult a professional first.
Mayflies on the car
If you have mayfly swarms around your car, you can consider using a mix of the above natural approaches to repelling them.
Spraying down with garlic oil or other essential oils may just be enough to keep them off your vehicle.
You can also spray them down directly with a strong hose to quickly rinse them off.
Mayflies in the aquarium
You’ll notice that their elongated body allows them to “wiggle” through water if you’ve ever seen mayfly larvae in your fish tank as a pest.
Because aquarium plants are widely traded and unregulated, you may end up with mayflies hitchhiking into your fish tank and may not even notice them as they’re hiding most of the day.
You may see them blaze across the water here and there, but they’ll hide between cracks and objects in your aquarium.
The easiest way to get rid of them from your fish tank would be to catch them with a net. Although they’re fast, you can watch them swim across and land on an object. Get a net ready and “catch” them quickly.
Then kill and dispose of them when you take them out of the tank. You may need to do a teardown of your tank if you want to remove them as larvae, or you can wait until they sprout wings and let them fly out.
You’ll then have to kill them as flying pests around your home afterward.
Did you get rid of your mayfly problem?
That’s about it! That’s about all I have to offer on the topic of “how to get rid of mayflies.”
For those with swarms or live in a native mayfly area, you’ll have to get professional help to manage mayfly pests, as it’s nearly impossible to keep them under control without large-scale approaches.
I hope this guide has helped you on your journey to get rid of mayflies.
If it did, please leave a comment and let me know! For those who’ve had experience with these pests, share your tips below!
And lastly, if you have a specific question you want me to review, go ahead and ask!
Thanks for reading!
Currently an active researcher in the pest control industry for the past 8 years- with a focus on using natural and organic methods to eliminate pest problems.
I share handy DIY pest techniques I come across here to help out others (and possibly save them from a mental breakdown).
Fight nature with nature.