Insects and us: a mind-blowing 20 quadrillion ants and what they mean for the planet | Insects

To Most of us, they are small, uninteresting and sometimes annoying, but 2022 revealed how ubiquitous ants are and how essential they are to the planet. Scientists revealed in September that there are 20 trillion (or 20 million billion) ants worldwide, or 2.5 million for every person on the planet.

The more than 12,000 known species of ants live in all kinds of habitats, from the Arctic to the tropics, and represent one of the most diverse, numerous and specialized groups of animals on the planet. Leafcutter ants are fungal farmers, enslaver ants capture their young to increase their labor force, while wood ants carry aphids to the succulent parts of the plant to collect their honeydew.

Dr. Sabine Nooten and Dr. Patrick Schultheiss, behavioral scientists at the University of Würzburg who were the lead authors of the study, have created a global map of ant abundance and are now investigating how ants have been affected by factors such as climate, habitat destruction. , urbanization and agriculture.

“Can any of these things cause larger or smaller numbers of ants?” Nooten asks. “Some studies last 80 years, so we can extrapolate to the future to see [what might happen to ants if] the environment changes so much again.’

The narrow-headed ant (Formica ecta) cares for birch aphids.
Some predatory ants have the potential to be used in pest control and may be more successful than existing chemical treatments. Photo: John Walters/PA

The two scientists point out that if the numbers of ants in a place are not known, as is the case in much of Africa, nothing else about those ants will be understood. “Diversity could exist in social structure, genetic or chemical diversity; this is all the stuff we’re still finding,” says Schultheiss.

Ants (Formicidae) are social animals that often live in complex colonies underground, in mounds or in trees. Each army of ants is led by a queen who lays thousands of eggs, and most of the ants seen from the ground are female workers, whose role is to mate with a new queen before the males die. Then the new queen will start a new colony.

Experts agree that ants are ecosystem engineers because they play a crucial role in breaking down organic matter, recycling nutrients, improving soil health, eliminating pests and dispersing seeds. But historically, ants have not attracted as much attention as crop pollinators, such as bees, who may have obvious economic value. That bias may soon change. Ants have been used as a biological pest on citrus crops in China for centuries, and research published in August indicates that the pest control powers of some predatory ants may work better than some agricultural chemicals.

The wonder of ant biology offers many other possibilities for real-world applications. Queen ants that live more than 30 years, but have the same genetic material as a short-lived worker ant, can teach us something about senescence. No one understands how queens store sperm inside their bodies for decades without any degradation, even though colonies live in different climates. In the meantime, Schultheiss’ research into ants’ navigation — how they find food and how they behave when lost — could help build mathematical models that teach a robot that’s looking for lost people.

A leafcutter queen ant surveys her colony.
The resilience of ants and their complex colonies may provide insight into the climate crisis. Photographer: Doug Schnurr/Alamy

Looking back at how ants have evolved can also shed light on a wide range of other plants and animals. Butterflies that rely on ants to care for their caterpillars could disappear if those ants were eliminated, says Corrie Moreau, a professor at Cornell University: “Nature is this intricately woven tapestry, and if you pull one thread, you’ll never know which is the critical thread that pulls it all down.”

When Moreau, an expert in myrmecology (the study of ants), studied under the famous biologist Edward O Wilson, he remapped the ant family tree and found that the evolution of ants is closely related to that of plants. “As flowering plants spread around the world, ants took advantage of this amazing ecological niche to start hunting new insects and to care for sap-sucking insects for honey, and the plants developed specialized structures to keep the ants there, including sugar water fountains and domestication. [hollow chambers in the plant where ant colonies can live]”.

Moreau’s observations while dissecting thousands of ants under the microscope lead to a new path of research. “The ants were the hardest to crack, with the hardest armor, the gut microbes that were either predators or herbivores,” says Moreau, who has used antibiotics to wipe out the bacteria in the ants’ guts and make the bacteria synthesize essentials. amino acids but that the ant host is penetrating the cuticle, the protective and flexible layer that surrounds the ant’s body.

A very sharp and detailed analysis of many images stacked with a microscope objective in a very sharp photograph of an Ant's head.
“We are just beginning to realize their ecological importance”, says Corrie Moreau about the humble ant. Photo: Tomas Rak/Alamy

This research could shed light on our gut microbiomes. “We can’t experiment with antibiotics on humans, then open them up and see what happens to the gut. But ants are social organisms like us, we can manipulate their simplified gut system, then see what happens. How quickly a pathogen gets in and spreads through a nest. we can see. In a social system, is there an area where if that happens, everyone gets infected? Are there social mechanisms that limit the transfer of these microbes? We can use ants to ask those questions.”

“Ants are going to be one of the critical systems to study in understanding the impacts of climate change … not just because of what’s disappearing, but because of what’s resilient,” says Moreau. “We are just beginning to realize their ecological importance.”

Every ant scientist has a favorite species

Australian desert ant (Melophorus wagon)
“At first glance, this cute big brown ant is nothing special, but they can use the sun’s position as a compass signal and learn to use visual landmarks like we do. [to navigate], so they notice a large tree on the left or a small bush on the right. They are fascinating,” says Patrick Schultheiss.

Florida tortoise ant (Cephalotes varians)
“These ants live in hollow branches in the crown and the soldiers block the entrance to the nest with their huge saucer heads and move to the side when they are ready to take another person from their nest,” says Corrie Moreau.

Green head ant (Rhytidoponera metallica)
“They have this amazing structural color, bright metallic green-blue-purple. And if you go to a picnic, he’s the first one to come, he’s brave!’ says Sabine Nooten.

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