the flies

For every person that inhabits this planet there are 17 million flies. These insects pollinate plants, devour decomposing corpses, eat the waste from our drains, damage crops, spread diseases, kill spiders and hunt dragonflies.

Some flies have even lost their wings to live exclusively on bat blood and spend their lives sneaking into the fur of their guests, leaving only to give birth to a single larva.

"That's why I love them: they do everything. They reach all places, without them there would be no chocolate, for example. McAlister hates chocolate but he loves the kind of fly that pollinates the cacao plant: a variety of midge. Gnats are tiny insects that feed mainly on blood, but chocolate gnats like nectar and transport pollen from one plant to another.

In fact, gnats are part of McAlister's specialty. She adores all the flies but focuses on the diptera that are at the bottom of the group, which includes mosquitoes, black flies and what she describes as "everything that stings, stings and is ugly."

His life among the flies includes both work in the museum and field research. This is the job of your dreams. McAlister remembers the first time he was behind the scenes in the museum, as a student, before working here. "They let me into a building that had 34 million insects. I said: 'Oh, how are you, I like them pretty well.' "

McAlister's fascination began during his childhood. "I used to take the fleas off the cats," he said and said he watched them with a microscope that his parents had given him. But soon it happened to more horrifying insects.

The decomposing corpses of some small creatures, which were also courtesy of the cats, were the hidden treasures of the cresas (set of insect eggs) with which it continues to delight. "I really like the dark side of nature," he said, just before starting to talk about the life of flies that kill spiders.

The larvae "throw themselves on the spiders" to land on them and dig into their abdomen. Then they eat the spider from the inside out. But if the spiders have not matured, the larvae go into hibernation for a few years until the spider grows into a banquet.

Many flies do a great favor to the planet - and to us - by cleaning all kinds of biological waste, from useless things to the slime of the pipes. The drainage flies, called psychodids, are actually dedicated to cleaning up the filth of the human being. But sometimes there is a demographic explosion that causes adults to emerge, which is very annoying; If the bodies disintegrate into small particles in the air, they become potentially harmful to human health.

And, of course, there are flies that feed on corpses: the 1100 different species of blowflies, the favorite flies of the detective programs. The crests of those flies, like the attractive blue fly larva, devour the corpses of mice, men and everything else.

Knowing which species lay their eggs and during which stage of decomposition can help determine when a person became a corpse.