10 Horrible Facts About Flies That Will Make You Scare

According to one 2016 survey, some 25% respondents reported a fear of insects. For many of us, they're downright terrifying. And among insects, flies are among the most annoying. They're everywhere, they can bite and spread disease, and some species, like botflies, are notorious for implanting maggots in your flesh. Gross! But if you're still not convinced that flies are worth your fear, let's take a look at some of the other scary things flies bring with them.

10. Some flies induce vomiting to dry out the contents of their stomach.

If you watched "Fly" David Cronenberg, you've learned the basics of '80s special effects detailing how a fly eats. They don't actually have a mouth designed for chewing like mammals, so instead they vomit things up to have their stomach acid pre-digest them, then swallow them through their straw-like mouths.

On a small scale, flies do this all the time, almost every time they land, including your food or the food you eat. But it’s not always because they’re trying to eat you and your dinner. Sometimes it’s just to aerate their last meal. Flies vomit because they obviously have small stomachs. They vomit the contents upward so that they can partially dehydrate in the open air. Less moisture means it takes up less space, so they can eat even more.

9. Flies can lay eggs in your eyes.

You've probably read or seen videos of botflies in the past. These flies can lay eggs on animals, including humans, and the larvae hatch inside your body, then grow bigger and creepier inside you until they're removed or crawl out on their own. It's pretty gross to watch and probably even worse to experience. But it's probably the best thing about botfly control. Because some species don't just want to grow in your arm or leg.

Species such as the sheep botfly and the Russian botfly have been known to implant their eggs in human eyes. The resulting condition, called ocular myiasis or internal ophthalmomyiasis, can lead to blindness. In 2022, doctors in France had to remove a dozen larvae from the outer layer of a person’s eyeball. Keep in mind that the larvae also have spines on them to prevent them from being pulled out.

8. Brazilian species of flies have inverted genitals

How much do you know about how flies mate? You're about to learn more than you wanted to know. It turns out that Brazil is home to a cave fly known as Neotrogla curvata This fly does things in the most unexpected way, that is, they mate for dates at a time, and the female uses a spiked penis to penetrate the male and stick to his insides so that she cannot free herself.

After 40 to 70 hours of being together, the male delivers a packet of sperm that fertilizes the female, and from there on everything works as you would expect. If you tried to separate the flies before this mating session was over, the female's tight grip would actually cause the male to snap in half.

7. Coffin flies can live in a grave for several generations.

With a name like “coffin fly,” you’d think this insect would be at least a little creepy, and it is! Also known as scuttle flies and hump flies, these little pests feed on voracious carrion, including human corpses. The name “coffin flies” comes from the fact that these critters can be found inside sealed coffins, feeding on the rotting remains. They can burrow six feet into the ground in search of food. That’s the equivalent of a human digging two miles to eat.

Once they are in the coffin, the flies will lay eggs and the maggots will begin to eat the remains. They seem to prefer lean tissue rather than fat and can reproduce for generations in a sealed coffin, feeding on the remains of their host until there is nothing left for them to eat. In terms of what this means in terms of days and weeks, the flies were breeding on a body that had been dead for 18 years. The crypts were opened after people noticed the flies outside and found the inside full of flies.

6. Deer flies can transmit deadly bacteria and diseases

House flies are annoying, but ask anyone in the horsefly and deerfly world which is worse and you won't find out. Deer flies bite and feed on blood. If you get caught in a swarm while hiking, you'll come home with holes in your body and possibly scars.

In addition to physical damage, deer flies can also carry all sorts of horrible diseases, parasites, and bacteria, including anthrax, hog cholera, tularemia, anaplasmosis, and Lyme disease among several others.

5. Skipper flies can eat bones

Competing with our friend the coffin fly is the bone skipper fly. While coffin flies prefer to feed on the lean tissues of a corpse, the bone skipper takes the complete opposite route and eats the bones.

With a round yellow-orange head, the flies are very noticeable, and their behavior is also notable. Not only do they prefer food that is already in the advanced stages of decomposition, they are also very active in winter, unlike other flies that prefer warmer weather. They were also thought to be extinct for over a century.

Aside from their dietary habits, their name comes from the fact that the flies have a habit of jumping on the bodies they are in, and in large enough groups they look like they are jumping all over the bones. This is how the larvae move, by twisting and quickly untwisting their body to jump.

Flies feed and reproduce in the marrow of crushed bones, so they prefer larger animal carcasses.

4. Fly vomit can be worse than fly bites.

We’ve already talked about fly vomit once, but there’s a lot more to say! For example, in addition to being extremely disgusting, it’s also potentially very dangerous. Probably more so than most of us realize. Research has shown that the common housefly may be much better at infecting humans than we previously thought. Most research on flies and the diseases they cause has focused only on flies that bite. But vomit from non-biting flies can contain bacteria from feces, dead bodies, rotting food, and sewage.

We mentioned vomit bubbles earlier, and that's where the problem comes in. They're constantly bubbling up all this bacteria, so whenever you see a fly on your food, on your furniture, or on you, that's what they're doing. Flies and the bacteria they spread haven't been studied much yet because research is limited. But there is some evidence that flies may actually promote the growth of antibiotic-resistant bacteria, making it even more difficult to fight the diseases they cause.

3. A species of fly has evolved to live in only two New York City parks.

Insects are generally very adaptable. This is partly because insects are better at taking advantage of evolution than humans. A housefly lives for about a month, but can reproduce up to 6 times a month. So there can be 5 generations in a month, and 60 in a year. It can take a million generations for evolution to produce significant, permanent changes in a species, so if a human generation is 30 years, then it would take 30 million years for evolution to occur. A housefly, on the other hand, takes a little over 16,000 years. That means it's much faster. Of course, this is all speculation, but the point is that flies can change pretty quickly, relatively speaking. For example, New York City's Central Park has its own flies.

Also found in Prospect Park but nowhere else, the New York species has evolved to thrive in the feces of waterfowl like ducks and geese. It would be difficult for such a species to thrive naturally in the wild, but residents routinely feed the birds in these parks, allowing the flies to thrive.

2. Flies perceive the world much more slowly than we do.

If you've ever had a fly in your house that gets on your nerves only to become more and more annoying as you try unsuccessfully to swat it, then you already know indirectly about flicker fusion.

We take it for granted that flies are really good at avoiding attacks, so when you try to swat them, especially with your bare hand, you often come up empty. They are too fast and too agile, and that is a result of the way their brains work.

In addition to all sorts of physical adaptations that give them speed in flight and running to safety, it may be hard to believe, but the fly brain is much better than the human brain when it comes to perception. Flies have a higher rate of flicker fusion than humans.

Flicker fusion refers to how many images your brain can process per second, which you can think of as the frame rate of your own thoughts. Flies have a flicker fusion rate that is 6 times faster than humans. In practical terms, this means that flies exist in a world that is much slower than ours. When you swing as fast as you can to swat a fly, it is able to perceive your movements 6 times better than you can, which to the fly makes you appear 6 times slower.

For a visual representation of this, you can check out the X-Men, of all things. There's a great scene in Days of Future Past where the character Quicksilver, who has superhuman speed, starts to take action, and the film is shot in such a way that it seems like the world around him is slowing down. Obviously, this is just a fun fictional representation, but maybe it's similar to how a fly would see the world.

1. Robot flies among us

If real-world flies weren't bad enough, science has been trying its best to imitate and improve on them with robotic flies that can serve a variety of purposes in the world at large.

The University of Washington created Robofly after 20 years of research into how to make something small and functional. This technology will allow tiny robots to access places that humans are too big to reach, and while they were no doubt designed for more altruistic purposes, search and rescue is certainly one of the main reasons for using a tiny robot like this, and by looking for things like gas leaks, you can easily see where they could become a problem. There's a saying about wanting to be a fly on the wall to eavesdrop on private conversations, and now you can literally put a fly on the wall to be used as a spy.

Firefly robots are another innovation in the world of flying bug robots. They were also designed with disaster rescue in mind, with the added aspect of using light as a form of communication to better coordinate rescue efforts if, for example, the flies found someone trapped in a collapsed building.

Various bug designs have been in development for several years, but it seems likely that it is only a matter of time before robot flies become commonplace. Or they may already be here.