11 Natural Predators That Eat Flies: In-Depth Look

Natural Predators That Eat Flies

When you hear the word “fly,” if you aren’t thinking about the act of flying, you’re probably thinking about the pesky bug that makes your home it’s own for several months a year. This large family of bugs has plenty of natural predators to keep them in line, making them less of a problem for you.

Flies in both their larval and adult form are a common food source for many animals. Below, we’ll cover some specifics about the life cycle of flies, what defenses they have evolved and how their predators have adapted to eat them.

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What Defense Mechanisms Does A Fly Have?

Fly in flight. Natural defense mechanisms of a fly.

The term “fly” refers to insects of the order Diptera, a collection of an estimated one million species, including common houseflies, pesky fruit flies, and the annoying horse-flies.

While flies are small insects, they still have various defense mechanisms to protect them from threats smaller than them and much larger than them.

Flys Have A Fast Reaction Time

If you’ve ever tried to swat a fly with your bare hand, odd are it had no problem flying off before you got to it. This is thanks to the reflex they have to be startled by visual movement, being able to react in under 50ms. For comparison, humans have a reaction time of 150-300 ms.

Flys react to people and see more images per second than people. Much like how a TV might refresh 60 times per second, human eyes can process 60 fps as well.

Flies React To Movement Quickly

Flies, on the other hand, can process 250 images per second. This incredible feat helps them react to even the smallest sudden movement in a fraction of a second to escape danger.

This reaction to sudden movement is the same idea that animals such as cattle and horses use to keep flies off them- by swishing their tail around to disturb the flies.

Flies Produce Lots Of Young

Texas A&M AgriLife Extension reports a female fly will lay up to 500 eggs over the course of three or four days.

That means that every fly that breeds is able to replace itself many times over, and it can afford to lose some along the way.

Female flies will choose an ideal location to lay their eggs, often choosing rotting fruits, vegetables, or meat as an option. Laying their eggs in a safe place that provides all the nutrients the maggots might need gives them their best chance at survival.

From Eggs To Adults Only Takes About A Week

The fly life cycle is the same as most insects and resembles a butterfly’s. The adult fly lays her eggs, when they hatch into maggots (larval stage), then pupate (similar to a cocoon), then emerges as an adult fly.

Depending on the temperature, fly eggs only take 8-12 hours to hatch. The maggots that emerge will then consume their surroundings and put that energy towards growing into a second and third larval stage, resembling the previous stage but larger.

The pupal stage is immobile, and the developing fly encases itself in a hard shell to help prevent predators.

This stage is different than how butterflies cocoon, as flies do not spin a silk casing around them, but the process of going from larval to adult stages of insects’ life is a shared function.

And not to make you shiver – but, flies actually may be laying eggs in your home if you seem to be having an abundance of flies and natural predators of them! For more information on fly eggs, and actually, where they may be laying them in your home, check out our article!

11 Natural Predators That Eat Flies

spider on a web surrounded by flies

Flies are an important part of the food chain in helping break down rotting food and as an important food source for many species of animals.

As annoying as flies might be to people, they are an important part of the environment.

The predators listed below help keep populations of these unwanted guests down and, in the wilderness, will feast on flies when given the chance, however, if it becomes an overwhelming issue we recommend calling a professional to assess your situation.

In fact, if you notice that you have a lot of other insects around, the reason may be that you have a large fly population present! The reason being? You may be attracting flies to your house without even knowing. Head on over to our article to learn more about what may be attracting flies to your space!

1. Fly Predators (A Parasite)

For a confusing start on a list of fly predators, there is a small parasitic insect called a Fly Predator. These predators target flies in the larval stage and don’t eat them but use them as a vessel to carry their young.

Fly predators will lay their eggs in a host pupa, and the eggs will soon hatch and eat the host from the inside out. While gruesome, this is an effective method to keep fly populations down.

If you have livestock and problems with flies, but don’t want to use fly predators, you can use a fly control feed additive such as the Farnam SimpliFly Feed Through Fly Control to prevent fly populations from building up.

2. Spiders Are The Best Known Fly Predator

Spiders are portable, the most well-known predator of flies, spinning intricate webs in high-traffic areas where flies get stuck. Once a fly is caught in a spider’s web, the spider will wrap them in silk and eat them later.

Spiders are responsible for eating hundreds of millions of tons of insects annually, and flies are one of the most prominent prey options for spiders.

Depending on the availability of insects, spiders can consume anywhere from one fly a week to four flies a day.

They Know Just How To Catch Flies

Not all spiders rely on webs for catching spiders, either. Some spiders will wait to ambush flies or hunt them down and attack when the fly does not expect it. Wolf spiders are one example of spiders using a hunting style to catch food.

While you might be arachnophobic, and afraid of spiders, they can be a beneficial insect to have around, helping to keep fly populations down.

Most species of spiders are not harmful to people either and can be a great addition to your home or at least something to keep outside.

And hey – even though spiders are really beneficial insects, we don’t always love seeing them! I mean they’re called creepy crawlers for a reason! If you notice a lot of spiders nearby, make sure to check out our spider-repelling guide.

3. Many Species Of Frogs Love To Eat Flies

Close up of a Horse-fly Tabanidae on a leaf

Flies might be able to react to move quickly, but frogs can shoot out their tongue even faster. Combined with special saliva that is super sticky, this makes frogs one of the best-adapted predators for eating flies.

Small species of frogs not much bigger than a thumbnail might target fruit flies, while larger species will eat house flies, horse flies, and any other flying insect they are able to get their hands- or tongue- on.

Frogs also benefit from camouflage that allows them to blend into their surroundings while they hold still and wait for flies to land within reach.

4. Lizards Are A Nimble Threat to Flies

Lizards are versatile threats to flies, coming in all shapes and sizes and living in different environments to eat any fly species.

Perhaps the best example of a lizard fly predator is the chameleon, able to shoot its tongue out up to four feet, the largest species.

The chameleon’s tongue is between one and two times its body length, and chameleons have pinpoint accuracy with it. Like frogs, they also have stick saliva that keeps the fly stuck to the tongue when retracting it.

5. Birds (Especially Chickens) Like To Eat Flies

Birds love to eat flies and their maggots, and chickens are especially adept at doing so.

Birds often pick through clumps of rotting foods where maggots may be found to dig out those tasty morsels and eat adult flies when given the chance.

Flies love to lay their eggs in piles of dung, such as cow patties or horse manure, and a few days later, birds often come by to search for food.

The dung has plenty of leftover nutrients for maggots to consume and grow, and these plump insects are perfect for birds.

This Actually Helps The Soil!

While searching for the maggots inside the feces, the birds will also spread out the manure, helping to disperse the nutrients over a larger area.

If you keep large animals on pasture, following them with chickens is a good way to control fly populations and keep the soil healthy.

In the wild, birds will go through animal corpses and piles of rotting plants in search of maggots and adult flies to eat. 

5. Bats Are An Insectivore Who Can Eat Hundreds Of Flies

Bats are well-known as mosquito eaters but will happily enjoy a variety of insects as a part of their diet. As the only flying mammal, bats are uniquely positioned to eat flying bugs like flies.

Most bats are either insectivores, herbivores who eat mainly fruit, or omnivores eating a combination of both.

Those insectivore bats will travel in groups, find large groups of insects, and swoop through the swarm to catch them from mid-air.

Flying insects and easy-to-catch larval forms of insects make up a large portion of the diets of many bats.

Bats Eat So Many Insects!

Bats can be responsible for eating their body weight in insects every night, which can be thousands of pesky bugs at a time.

As a form of pest control, bats are estimated to be worth more billions of dollars per year, not including their value as pollinators as well.

The next time you see a bat, remember to thank it for keeping bug populations down and helping to pollinate our crops.

6. Fish Are A Surprising Threat To Flies

Any fly landing on the surface of a lake or pond might be looking for a quick drink and instead is part of a fish’s lunch. Various species of flies compose a portion of fish diets, especially for smaller fish species.

In fact, fish are so attuned to eating flies that there is a method of fishing designed to mimic this- fittingly called fly fishing.

Flys are so lightweight they can use the surface tension of water to float on top, even in a light current, and fishermen will use fake flies to achieve the same results.

Even large trout and salmon cannot resist a helpless fly resting on the surface of the water, and will strike from underneath. Since flies can’t see underneath them very well, and the water influences their vision, they are easy for fish to catch.

The Archerfish Especially Loves Flies

One fish that is especially well adapted to catching flies is the archerfish. Native to Asia and Australia, the archerfish has become a common species in the aquarium hobby and has a unique hunting method.

The archerfish is able to accurately spit a stream of water up to five feet, knocking flys out of the air and other insects off of overhanging branches.

This puts otherwise safe insects in the range of the fish’s mouth.

7. Praying Mantises Are A Fly-Eating Machine

Praying mantises are one of the fastest-moving insects and the most powerful pound-for-pound. Using plenty of patience to stay still and camouflage until a fly is in range of its claws, then the mantis strikes.

Praying mantises are small and efficient with their food, so for most species, a single fly is all they need once or twice a week. Over time, however, this can equate to dozens of adult flies being taken out of the local ecosystem for each mantis.

A praying mantis can strike in 50 ms, which is the same as a fly’s reaction time. This speed is key for mantises to be efficient predators and allows them to start eating the fly before it knows what happened.

8. Opossums Eat More Bugs Than Just Ticks

Opossums might be well known for eating ticks and being immune to Lyme disease, but they will also eat any manner of insects. Maggots found, especially in the trash in urban environments, are a common part of the opossums’ diet.

Opossums are not picky eaters and are omnivores, so anything that might be edible will be eaten. This includes all insects, berries, trash, and anything else.

Possums related to opossums eat a very similar diet but are native to Australia, New Zealand, and China. On the other hand, opossums are native to North America and are also commonly referred to as possums, even though this is technically incorrect.

9. Dragonflies Are Fast-Flying Fly Hunters

Dragonflies are the fighter jet of the insect world, capable of flying 35 miles per hour, and are effective hunters of other insects. Compared to a house fly, with a top speed of five miles per hour, the difference in speed is astounding.

The only fly that is able to move faster than a dragonfly is the painful-biting horsefly, although its speed is not as consistent as the dragonfly. However, horseflies are still a part of the menu for dragonflies.

Dragonflies will consume between 10 and 15 percent of their body weight each day, helping to keep fly populations down and having no trouble catching them.

10. Other Insects Predate On Flys

fly on leaf

Besides dragonflies, there is a wide array of other insects that will eat flies. These predatory insects might eat eggs, maggots, or adult flies and have different adaptations to help them do so.

Parasitoid wasps, for example, will use maggots and adult flies as hosts, laying eggs inside them as a suitable environment for the eggs to hatch and feed. And, if you’re having a wasp problem we always recommend calling a professional, and checking out our guide on why wasps are around and how to get rid of them.

Assassin or robber flies are another species of flies that hunts other insects rather than behaving as scavenger species like most flies. This group of insects is comprised of several thousand species, some using colorful adaptations to blend in with other insects and some looking like normal flies.

Ladybugs and lacewings are effective predators of small species of flies, including fruit flies and black flies, among others.

Wrapping Up!

So there you have it, 11 natural predators that eat flies in both their adult and larval forms. Even with so many different predators that eat them, flies are able to maintain populations in the millions, even in a small amount of space.

For a quick recap, the main predators of flies include:

  • Fly Predators
  • Spiders
  • Lizards
  • Birds
  • Bats
  • Fish
  • Praying Mantises
  • Opossums
  • Dragonflies
  • Predatory Insects

So if you have a problem with flies this spring, take all the necessary steps to remedy the problem, and maybe leave a few of the animals on this list alone, and they’ll help keep the flies at bay.

Thanks for reading!

References

Bellezza Oddon, S., Biasato, I., Imarisio, A., Pipan, M., Dekleva, D., Colombino, E., Capucchio, M. T., Meneguz, M., Bergagna, S., Barbero, R., Gariglio, M., Dabbou, S., Fiorilla, E., Gasco, L., & Schiavone, A. (2021). Black soldier fly and yellow mealworm live larvae for broiler chickens: Effects on bird performance and health status. Journal of Animal Physiology and Animal Nutrition, 105(S1), 10–18.

Geden, C. J. (2021). Coleopteran and acarine predators of house fly immatures in Poultry Production Systems. Biocontrol of Arthropods Affecting Livestock and Poultry, 177–200.

Hieber, C., Wilcox, S., Boyle, J., & Uetz, G. (2002). The spider and fly revisited: Ploy-counterploy behavior in a unique predator-prey system. Behavioral Ecology and Sociobiology, 53(1), 51–60.

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