Generally speaking maggots (the larval stage of flies and other related insects) are absolutely disgusting, but they are also interesting things. And, they aren't ALL bad!
Maggots have anti-bacterial powers. Centuries ago, soldiers in the Middle East noticed that wounds with maggots in them healed faster and were cleaner than those without them. This gave birth to maggot therapy. It took hundreds of years, but nowadays some hospitals, mostly in parts of the world where antibiotics are not readily accessible, use maggot secretions as a substitute for antibiotics to clean wounds. Maggots are actually an FDA approved therapy.
Maggots are also used in forensic science. Insects usually enter a dead body within 24 hours of death and scientists can study the state of the maggots on a body and determine to what extent they have grown in the corpse. This technique allows the time of death to be estimated.
Clearly maggots fill a special niche. They are a vital part of the decay process because they eat bacteria and dead things. And, let's give credit where credit is due. The flies that lay maggots know where where to lay them so they will flourish and be the most effective.
Flies generally lay their eggs on things that are a good food source for maggots, so when the larvae hatch they can begin feasting immediately.
Over several days maggots eat, defecate, grow, and sometimes molt. At that point, the are usually creamy colored then they squirm off to a reasonably dry place, stop moving,and grow a dark shell. Inside the shell they transform into a fully formed insect. It takes about ten days from maggot to fly.
A maggot's front end has a mouth with hooks that help them grab food. Despite their voracious appetite they lack a sophisticated digestive system. So as they move through whatever it is they are eating, they secrete fluid containing digestive enzymes to help them dissolve their meal.
Fruit fly maggots, which are normally vegetarians, have cannibalistic tendencies. Once a maggot is injured, it’s fair game for other maggots! Scientists don’t know why the injured maggots get eaten.
A massive group of feeding maggots, combined with their digestive juices and all that writhing movement really heat generates heat...so much that the maggots will migrate to cooler spots. 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 104-122 degrees F.
Maggot researchers have discovered that some maggots have the ability to smell particular aromas and react to light. Fruit fly maggots can’t see distinct images, but they have eye-like photoreceptors that help them detect brightness. They also have light-sensing cells along their body. Both help protect them from too much light which can kill them. Maggots have just 21 odor-receptor neurons (compared to 1,300 in flies), but they are still able to detect a number of odors.
Back in the 18th century people commonly accepted the theory that maggots appeared spontaneously from non-living things. This was despite the fact that two centuries earlier, in 1668, Italian physician Francesco Redi conducted an experiment that debunked that theory. He showed that maggots turned into flies, which laid eggs that turned into maggots. He also observed that maggots only appeared on meat that was left uncovered.
Black soldier flies are particularly fast eaters that work their way through their food so fast that bacteria don’t stand a chance. This cuts down on odors produced by bacteria which cuts down on the stink produced during composting.
There is actually a maggot market and it is helping to solve the problem of over-fishing. The protein in most feed for commercial chickens, pork, and fish farms comes from fisheries which is a problem because some marine species depend on small fish as their food source. So instead of making animal feed from fish meal, it can be made from maggots.
Female black soldier flies lay about 500 eggs apiece and when these fast-eating maggots reach the pupa stage, they can be harvested, crushed, dried and turned into animal feed. This process has another benefit...it keeps more food waste out of landfills, decreasing methane emissions and water pollution.
If you ever eat pecorino cheese (a cheese made from sheep's milk) on your pasta, do you know it's story? On Sardinia, a sheep cheese called casu marzu, three weeks into the curing process gets the top crust cut off and the smell attracts what's known as “cheese skipper” flies which arrive and come lay their eggs.
A few weeks later, maggots hatch and begin eating their way through the cheese. The maggots digestive enzymes break the cheese down break making a contribution to the texture and flavor of the cheese. That’s when it’s ready to eat. The European Union has outlawed the cheese, but it's still made.
Rat-tailed maggots are also interesting. They are capable of surviving in filthy water, like that found in stagnant ponds, lakes, and drainage areas. They have very long tails, which are actually a 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.
Scientists have discovered that the surface of their bodies is actually covered with in 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 explains why these maggots thrive where other species can't.
Not all maggots feed on dead flesh. In the Galapagos Islands, the larvae of an invasive parasitic fly are threatening local bird populations. The flies can lay a couple hundred eggs in a bird nest and 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.