Paul Ventner via Wikimedia Commons // CC BY-SA 3.0
Paul Ventner via Wikimedia Commons // CC BY-SA 3.0

15 Facts About Maggots

Paul Ventner via Wikimedia Commons // CC BY-SA 3.0
Paul Ventner via Wikimedia Commons // CC BY-SA 3.0

Few things trigger revulsion like the sight of maggots writhing through rotting food or decomposing road kill. But maggots, which are the larval stage of flies and other related insects, are actually one of nature’s unsung heroes. Along with bacteria and other insects, they quickly break down dead things. Maggots provide other beneficial services as well, from helping solve crimes to healing wounds.

Of course, not all maggots perform such brilliant feats; some, for example, are pests that eat crops. But they don’t deserve the universally bad rap they’ve been given. So the next time your stomach lurches at the sight of maggots squirming, here are 15 examples to help you remember what amazing creatures they actually are.

1. THE LIFE CYCLE OF A MAGGOT IS PRETTY INTENSE.

Flies generally lay their eggs on things that will make a good food source for their offspring, so when maggot larvae hatch they can get to work feasting right away. Over several days they will eat, poop, grow, and sometimes even molt. At that point, the typically creamy colored maggots will pupate, meaning they’ll squirm off to a reasonably dry place, stop moving, and grow a dark shell.

Inside that shell, they transform from a mushy mass to a fully formed insect. In about 10 days, maggots will emerge from the pupal casing as hairy, bug-eyed flies and scamper off to mate, starting the cycle all over again.

2. THEY'RE VORACIOUS EATERS.

They have no legs, but their front ends have mouths with hooks that help them grab at decaying flesh and other delectable food items. Despite their endless appetites, however, they lack a sophisticated digestive system. So as they move through a corpse or rotten food, they secrete fluid containing digestive enzymes to help them dissolve their foul meal.

3. SOME MAGGOTS EAT OTHER MAGGOTS.

In 2013, researchers from the University of Lausanne published a study reporting that fruit fly maggots—normally vegetarians—actually have cannibalistic tendencies. Once a maggot is injured, it’s fair game for a feeding frenzy. Why would a normally vegetarian species do such a thing? Scientists don’t have clear answers yet, but their research studying maggots could help answer basic evolutionary questions about cannibalism.

4. THEY GENERATE A LOT OF HEAT.

Maggots feed in massive groups, and all those digestive juices and movement can really heat up their immediate environment. They deal with this by retreating to cooler spots when the temperature becomes uncomfortably hot. But research suggests that if you put enough maggots in a confined space and wait, eventually the temperature will rise to the point that they’ll start to die—somewhere between 104F° and 122F°.

5. MAGGOTS RESPOND TO LIGHT AND ODORS.

Maggots aren’t the most sophisticated creatures, but research shows some have the ability to smell particular aromas, as well as react to light. Fruit fly maggots can’t see distinct images, but they have eye-like photoreceptors known as Bolwig organs that help them detect brightness. More recently, researchers discovered they also have light-sensing cells along their body. Both help to protect them from too much light, which can be deadly for young fruit flies.

Meanwhile, other researchers have focused on studying maggots’ sense of smell. According to Matthew Cobb, a biologist at the University of Manchester in the UK, maggots have just 21 odor-receptor neurons, compared to 1300 in flies and millions in more complex animals like rats and people. In spite of this, maggots are still able to detect a surprising number of odors.

6. PEOPLE USED TO BELIEVE THAT MAGGOTS SPONTANEOUSLY APPEARED FROM NOTHING.

Science has come a long way since the 18th century. Then, people commonly accepted the theory of spontaneous generation—a belief that life could develop from non-living things, despite the fact that some two centuries earlier, in 1668, Italian physician Francesco Redi conducted a low-tech but effective experiment that showed otherwise. Redi demonstrated that maggots turned into flies, which laid eggs that turned into more maggots. He observed that maggots only appeared on meat that’s left uncovered, allowing flies to lay eggs that later hatched.

7. THEY CAN HELP SOLVE CRIMES.

We all know from our favorite TV shows that establishing the time of death is a fundamental part of a murder investigation. The time of colonization—as in, the moment at which flies arrive and begin feeding and laying eggs in decomposing flesh—helps forensic entomologists more accurately assess time of death.

It only takes a few minutes for some species of flies to begin arriving and laying eggs. So by noting the various species present and studying the age of the maggot offspring squirming around in a body, it’s possible to determine the minimum amount of time that’s passed since death.

8. MAGGOTS CAN ALSO SAVE LIVES.

Surprisingly, some species are quite effective at helping wounds heal and inhibiting infection. So-called maggot debridement therapy isn’t a new technology; it’s been observed for centuries that soldiers injured in battle often healed faster when their wounds were infested with maggots. Orthopedic surgeon William Baer, who had observed this himself in World War I, presented a groundbreaking study in 1929 showing that children with osteomyelitis (bone infection) and soft tissue wounds could be successfully treated with maggot therapy.

During the subsequent decade, thousands of doctors used maggot therapy. But the rise of antibiotics, coupled with challenges in obtaining medical-grade maggots grown in completely sterile conditions, saw the treatment dwindle. That’s changing, however, with the rise of antibiotic resistance and an increased prevalence of chronic diseases like diabetes that lead to non-healing wounds. Today, maggot therapy is making somewhat of a comeback.

9. MEDICAL MAGGOTS ARE AN FDA-APPROVED TREATMENT.

Maggots used in debridement therapy feed exclusively on rotting flesh. They help clear out the dead, bacteria-infested tissue of a wound so that healthy tissue can thrive and the wound can close. They leave healthy flesh alone. But there’s more to it than that. Maggots help curb inflammation by suppressing a part of the body’s immune system response.

Inhibiting the immune system might sound counterintuitive, but it turns out that maggots secrete a fluid capable of breaking down proteins that can trigger an overactive immune response. That overreaction by the immune system can lead to chronic inflammation, which in turn slows down healing and can increase the likelihood of infection.

In 2004, the U.S. Food and Drug Administration approved the use of medical maggots. They are typically placed in small, permeable packages and applied to the wound so that they can do their thing without crawling away (or into the body).

10. MORE TYPICAL USES FOR MAGGOTS INCLUDE HELP WITH COMPOSTING.

If you’ve ever waited too long to take the trash out in the middle of summer, you may have lifted up the lid and been repulsed at the sight of maggots writhing through last week’s leftovers. But they are actually excellent for creating rich, nutrient-laden compost.

Black soldier flies (rising stars of the maggot world—see below) are particularly speedy eaters. They work their way through organic food and animal waste so quickly that bacteria don’t stand a chance. This cuts down on odors produced by bacteria. So, bonus: your compost won’t smell as bad when these maggots are at work en masse.

11. THERE'S MONEY IN MAGGOTS.

From Colorado to South Africa, the maggot market is heating up—and helping to solve the problem of overfishing. Right now, the protein in most feed for commercial chickens, pork, and fish farms comes from ocean fisheries like sardines and herring, many of which are collapsing. That’s a huge problem, because other marine species depend on these tiny fish as their major food source. So instead of making commercial animal feed from fish meal, some forward-looking entrepreneurs are turning to farming maggots.

On a maggot farm, female black soldier flies lay about 500 eggs apiece [PDF]. This produces an army of hungry maggots that eat their way through mounds of food waste. And boy, do they eat fast. Once these plump maggots reach the pupa stage, they can be harvested—crushed, dried, and turned into animal feed. Besides protecting marine life, this keeps more food waste out of landfills, decreasing methane emissions and water pollution.

12. IN SARDINIA, MAGGOT-INFESTED CHEESE IS A DELICACY.

Ever enjoyed a dusting of Pecorino cheese on your pasta? On the Mediterranean island of Sardinia, a sheep cheese called casu marzu starts out in much the same way as Pecorino (a cheese made from sheep's milk). But then, three weeks into the curing process, the top crust is cut off, and the ripening aroma beckons to “cheese skipper” flies to come and lay their eggs.

A few weeks later, maggots hatch and begin working their way through the stinky cheese. And that’s where the magic—if you can call it that—happens. The maggots break it down with their digestive enzymes, making a special contribution to the cheese’s texture and flavor. And that’s when it’s ready to eat. The flavor of casu marzu has been described as something like a strong gorgonzola or Stilton. The European Union has outlawed it, but a handful of farms on the island still make it in the traditional way.

13. A SCIENTIST RECENTLY MADE A VIDEO OF HIS BOTFLY INFESTATION TO ILLUSTRATE THE INSECT'S LIFECYCLE.

In the tropics of Central and South America, Dermatobia hominis botflies frequently lay their tiny eggs on mosquitos. When a host mosquito lands on a warm human, body heat triggers the eggs to drop onto the skin. After they hatch, the itty bitty larvae worm their way deep under the skin and grow tiny spines that allow them to hang on tight. The parasites also release a painkilling agent to make their presence less noticeable. Sounds fun, doesn’t it?

It gets worse. Harvard entomologist Piotr Naskrecki got infected with botflies while leading a nature photography workshop in Belize. It wasn’t the first time, either, so he knew what to expect. As Naskrecki describes in his blog, he decided to let two of the larvae develop under his skin. He knew in a few weeks the larvae would grow to the size of a peanut, and pop out of his body to continue their transformation as pupae. You know, no big deal.

His reward was getting to photograph and film the invaders as they emerged from his skin, and document their transformation into flies. If your stomach is still feeling steady, you can watch the video here.

14. SOME MAGGOTS HAVE TAILS.

Rat-tailed maggots—how’s that for a name—are capable of surviving in very dirty water, like that found in stagnant ponds, lakes, and drainage areas. They get their name from their very long tails, which are actually a sort of tube that allows them to breathe under water. They are the larval stage of a drone fly, which is also known as the bee fly because of its resemblance to a honey bee.

The larvae’s tough outer covering may help protect them from bacteria present in the dirty water. But recently, scientists have discovered that there’s something else going on: the surface of their bodies is actually covered in nanopillars, spiny projections that make it difficult for bacteria in the water to congregate on the larvae. The researchers theorize that these may inhibit bacterial infection, which would explain why the maggots thrive in stagnant, dirty water where other species cannot.

15. A PARASITIC MAGGOT IS WREAKING HAVOC ON BIRDS IN THE GALAPAGOS.

Not all maggots feed exclusively on dead flesh. In the Galapagos Islands, the larvae of an invasive parasitic fly called Philornis downsi are threatening local bird populations. At least 16 of 20 species endemic to the Galapagos are in trouble because of the fly, including the famed Darwin’s mangrove finch. The flies can lay a couple hundred eggs in a bird nest. When the maggots hatch, they crawl up into baby birds’ orifices and suck their blood. Eventually the chicks die, and the maggots then feed on their corpses.

A team of scientists is working on eradicating P. downsi in the Galapagos by breeding masses of sterile male flies that can be released on the islands. As the sterile males mate with females, the population of flies should begin to drop.

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How Does Catnip Work?
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If you have a cat, you probably keep a supply of catnip at home. Many cats are irresistibly drawn to the herb, and respond excitedly to its scent, rubbing against it, rolling around on the floor, and otherwise going nuts. There are few things that can get felines quite as riled up as a whiff of catnip—not even the most delicious treats. But why does catnip, as opposed to any other plant, have such a profound effect on our feline friends?

Catnip, or Nepeta cataria, is a member of the mint family. It contains a compound called nepetalactone, which is what causes the characteristic catnip reaction. Contrary to what you might expect, the reaction isn’t pheromone related—even though pheromones are the smelly chemicals we usually associate with a change in behavior. While pheromones bind to a set of specialized receptors in what’s known as a vomeronasal organ, located in the roof of a cat's mouth (which is why they sometimes open their mouths to detect pheromones), nepetalactone binds to olfactory receptors at the olfactory epithelium, or the tissue that lines the mucus membranes inside a cat’s nose and is linked to smell.

Scientists know the basics of the chemical structure of nepetalactone, but how it causes excitement in cats is less clear. “We don’t know the full mechanisms of how the binding of these compounds to the receptors in the nose ultimately changes their behavior,” as Bruce Kornreich, associate director of the Cornell Feline Health Center, tells Mental Floss. Sadly, sticking a bunch of cats in an MRI machine with catnip and analyzing their brain activity isn’t really feasible, either from a practical or a financial standpoint, so it’s hard to determine which parts of a cat’s brain are reacting to the chemical as they frolic and play.

Though it may look like they’re getting high, catnip doesn’t appear to be harmful or addictive to cats. The euphoric period only lasts for a short time before cats become temporarily immune to its charms, meaning that it’s hard for them to overdo it.

“Cats do seem to limit themselves," Michael Topper, president of the American Veterinary Medical Association, tells Mental Floss. "Their stimulation lasts for about 10 minutes, then it sort of goes away.” While you may not want to turn your house into a greenhouse for catnip and let your feline friend run loose, it’s a useful way to keep indoor cats—whose environment isn’t always the most thrilling—stimulated and happy. (If you need proof of just how much cats love this herb, we suggest checking out Cats on Catnip, a new book of photography from professional cat photographer Andrew Martilla featuring dozens of images of cats playing around with catnip.)

That said, not all cats respond to catnip. According to Topper, an estimated 70 percent of cats react to catnip, and it appears to have a genetic basis. Topper compares it to the genetic variation that causes some individuals to smell asparagus pee while others don’t. Even if a cat will eventually love the smell of catnip, it doesn’t come out of the womb yearning for a sniff. Young kittens don’t show any behavioral response to it, and may not develop one until several months after birth [PDF].

But some researchers contend that more cats may respond to catnip than we actually realize. In one 2017 study, a group of researchers in Mexico examined how cats might subtly respond to catnip in ways that aren’t always as obvious as rolling around on the floor with their tongue hanging out. It found that 80 percent of cats responded to catnip in a passive way, showing decreased motor activity and sitting the “sphinx” position, an indicator of a relaxed state.

There are also other plants that have similar effects on cats, some of which may appeal to a wider variety of felines than regular old catnip. In a 2017 study in the journal BMC Veterinary Research, researchers tested feline responses to not just catnip, but several other plants containing compounds similar in structure to nepetalactone, like valerian root, Tatarian honeysuckle, and silver vine. They found that 94 percent of cats responded to at least one of the plants, if not more than one. The majority of the cats that didn’t respond to catnip itself did respond to silver vine, suggesting that plant might be a potential alternative for cats that seem immune to catnip’s charms.

Despite the name, domestic cats aren’t the only species that love catnip. Many other feline species enjoy it, too, including lions and jaguars, though tigers are largely indifferent to it. The scent of the plant also attracts butterflies. (However, no matter what you’ve heard, humans can’t get high off it. When made into a tea, though, it reportedly has mild sedative effects.)

The reason Nepeta cataria releases nepetalactone doesn’t necessarily have to do with giving your cat a buzz. The fact that it gives cats that little charge of euphoria may be purely coincidental. The chemical is an insect repellant that the plant emits as a defense mechanism against pests like aphids. According to the American Chemical Society, nepetalactone attracts wasps and other insect predators that eat aphids, calling in protective reinforcements when the plant is in aphid-related distress. That it brings all the cats to the yard is just a side effect.

Because of this, catnip may have even more uses in the future beyond sending cats into a delighted frenzy. Rutgers University has spent more than a decade breeding a more potent version of catnip, called CR9, which produces more nepetalactone. It’s not just a matter of selling better cat toys; since catnip releases the compound to ward off insects, it’s also a great mosquito repellant, one that scientists hope can one day be adapted for human use. In that case, you might be as excited about catnip as your cat is.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Good News, Dog Parents: You Can Teach Puppies as Well as Their Canine Moms Can
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If you’ve ever adopted a puppy, you probably know how frustrating it can be to teach your new family member the basic tenets of common decency, like not to pee on the carpet or tear up a whole roll of toilet paper.

In other areas, though, pups are rather impressive learners, capable of mimicking some human behaviors. In fact, for some tasks, they learn just as effectively from watching people as they do from watching other dogs, including their own mothers, a new study in Nature revealed.

Researchers from Hungary and the UK took 48 young puppies of various breeds and studied the conditions under which they can be taught to open a puzzle box containing food. The experiment revealed that the puppies were able to learn how to open the box regardless of whether the task was first demonstrated by a person, their mother, or an unfamiliar dog. In other words, not only are puppies capable of social learning, but they're able to learn tasks from humans they don't know—in this case, the experimenter.

However, researchers were surprised to learn that the puppies were more likely to learn how to open the box by watching an unfamiliar dog than by watching their own mothers. That may be because puppies spend more time looking at—and thus, learning from—an unfamiliar dog that intrigues them. This differs from other species such as kittens, which “learn to press a lever for food more rapidly from their mother than from an unfamiliar adult,” the study notes.

In addition, the puppies were able to perform the task again after a one-hour break, indicating that they had retained some memory of the learning experience.

The ability of dogs to learn from humans has been recorded in previous research. A 2015 study revealed that dogs learn better by demonstration (or the “do as I do” method) than training techniques that involve a system of punishments and rewards. The "do as I do" approach probably isn't the most practical method of teaching your pup to do its business outside, but if you already have an adult dog at home, your new puppy can follow the older dog's lead and learn by example.

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