According to one 2016 survey, approximately 251,000 respondents reported a fear of insects. Many of us are downright terrified of them. And among insects, flies are among the most unpleasant. They're everywhere, they can bite and spread diseases, and some species, like botflies, are notorious for implanting maggots in your flesh. Gross! But if you're still not convinced flies are worth your fear, let's take a look at some more of the terrifying things they bring with them.
10. Some flies induce vomiting to dry out the contents of their stomach.
If you watched «"Fly"» David Cronenberg, you've memorized the basics of '80s special effects detailing how flies eat. They don't actually have mouths designed for chewing like mammals, so instead they vomit things to be pre-digested by their stomach acid, then swallow them through their straw-like mouths.
On a small, real-world scale, flies do this constantly, almost every time they land, including on 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 simply to aerate their last meal. Flies vomit because they obviously have small stomachs. They vomit their contents upward so they can partially dehydrate in the open air. Less moisture means it takes up less space, so they can, in turn, eat even more.
9. Flies can lay eggs in your eyes.
You've likely 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 larger and creepier inside you until they're removed or emerge on their own. It's incredibly unpleasant to watch and probably even worse to experience. But it's perhaps the best outcome of 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 are 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 to prevent them from being removed.
8. Brazilian fly species have inverted genitals.
How much do you know about how flies mate? You're about to learn more than you ever 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, meaning they mate for dates at a time, and the female uses a spiked penis to penetrate the male and stick to his insides so she can't escape.
After 40-70 hours of mating, the male delivers a sperm packet that fertilizes the female, and from that point on, everything works as expected. If you tried to separate the flies before this mating session ended, the female's tight grip would actually cause the male to split 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! These little pests, also known as scavenger flies and hump flies, 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 rotting remains. They can burrow six feet into the ground in search of food. This is the equivalent of a human digging two miles to find a meal.
Once they enter the coffin, the flies lay eggs, and the maggots begin to feed on the remains. They seem to prefer lean tissue over fat, and can reproduce for several generations in a sealed coffin, feeding on their host's remains until there's nothing left to eat. In terms of days and weeks, this means the flies were breeding on a body that had been dead for 18 years. The crypts were opened after people noticed flies outside and discovered the entire interior was infested with flies.
6. Deer flies can transmit deadly bacteria and diseases
Houseflies are annoying, but ask anyone in the world where horseflies and deerflies live which is worse, and you won't find out. Deerflies bite and feed on blood. If you get caught in a swarm while hiking, you'll return 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 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 bones.
With their round, yellow-orange heads, these flies are very noticeable, and their behavior is also distinctive. Not only do they prefer food that is already in the advanced stages of decomposition, but 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.
Beyond their dietary habits, their name comes from the fact that flies have a habit of jumping on the bodies they inhabit, and in large enough groups, they appear to be jumping all over the bones. This is how the larvae move: by twisting and rapidly untwisting their bodies to hop.
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, but there's much more to say! For example, besides being utterly disgusting, it's also potentially very dangerous. Probably more so than most of us realize. Research has shown that common houseflies may be much more adept at infecting humans than we previously thought. Most research on flies and the diseases they cause focuses only on biting flies. But vomit from non-biting flies can contain bacteria from feces, carcasses, rotting food, and sewage.
We mentioned vomit flies earlier, and that's where the problem arises. They're constantly bubbling up all this bacteria, so whenever you see a fly on your food, your furniture, or on you, that's what they're doing. Flies and the bacteria they spread haven't been widely studied yet, because research is limited. But there's some evidence that flies may actually promote the proliferation of antibiotic-resistant bacteria, making it even more difficult to combat 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 they exploit evolutionary advantages better than humans. A housefly lives for no more than a month, but can reproduce up to six times a month. This means there can be five 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 evolution would take 30 million years. A housefly, on the other hand, requires just over 16,000 years. This means it's much faster. Of course, this is all speculation, but the point is that flies can change quite quickly, relatively speaking. For example, New York City's Central Park has its own species.
Also found in Prospect Park, but nowhere else, the New York species has evolved to breed in the feces of waterfowl, such as ducks and geese. It would be difficult for such a species to thrive naturally in the wild, but residents regularly 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 truly adept at evading attacks, so when you try to swat them, especially with your bare hand, you often come up empty. They're too fast and too agile, and that's a result of how their brains work.
In addition to all sorts of physical adaptations that give them speed in flight and sprinting to safety, it may be hard to believe, but a fly's brain is far superior to 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 six times higher than humans. In practical terms, this means flies exist in a world that's much slower than ours. When you swing as fast as you can to swat a fly, it can perceive your movements six times better than you can, which makes you appear six times slower to the fly.
For a visual representation of this, you can check out X-Men, of all things. There's a great scene in Days of Future Past where the character Quicksilver, who possesses superhuman speed, starts acting, and the film is shot in such a way that it seems like the world around him slows down. Obviously, this is just a fun, fictional representation, but perhaps 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 scrambling 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 making something small and functional. This technology will allow tiny robots to access places that are too large for humans. While they were undoubtedly developed for more altruistic purposes, search and rescue is certainly one of the main reasons for using a tiny robot like this. Also, by looking for things like gas leaks, you can easily spot potential problems. 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 developed with disaster rescue in mind, with the added benefit of using light as a form of communication to better coordinate rescue efforts if, for example, the flies find someone trapped in a collapsed building.
Various beetle designs have been in development for several years, but it seems likely that robotic flies will become commonplace. Or perhaps they already exist.