Ants have been around since the Cretaceous Period, thriving for 100 million years before ruining a single picnic. They not only survived the asteroid that killed the dinosaurs; they spread out of tropical forests to pretty much conquer the world.
Today, up to 10 quadrillion ants are alive on Earth at any given time. Their total biomass weighs about the same as all 7.4 billion humans put together, and they exist almost everywhere, except - ironically - Antarctica.
"Ants are everywhere, but only occasionally noticed," biologist E.O. Wilson wrote in "The Ants," his Pulitzer-winning 1991 book about the insects. "They run much of the terrestrial world as the premier soil turners, channelers of energy, dominatrices of the insect fauna - yet receive only passing mention in textbooks on ecology."
Even after all this time, we're still digging up new secrets about ants. For a glimpse into their antics, here are a few of the most amazing things we know...so far.
1. Ant colonies act as 'superorganisms'
"Individual ants are the equivalent to the neurons in your brain - each one doesn't have a lot to say, but in combination they can get a lot of things done," entomologist Mark Moffett told Live Science in 2014. Ant colonies are considered "superorganisms," rallying hordes of individual workers to act as parts of a larger, more powerful entity.
In a 2015 study, researchers tested this idea by watching how ant colonies reacted to the abduction of scouts and workers. The ants were displeased in both cases, but their differing responses spoke volumes. "When scouts were removed from the periphery, the foraging 'arms' of the colony retracted back into the nest," the study's authors explain in a statement. "However, when ants were removed from within the center of the nest itself, the whole colony fled, seeking asylum in a new location."
What does this mean? If a colony is a superorganism, the first scenario is like recoiling your hand after burning it on a stove, the researchers say, while the second is akin to fleeing a house fire. "This suggests that colonies react differentially, but in a coordinated fashion, to these differing types of predation," they write. "Our findings lend support to the superorganism concept, as the whole society reacts much like a single organism would in response to attacks on different parts of its body."
2. Ants can form living bridges
On top of being expert builders, some ants are also excellent building materials. In the video above, army ants show off their uncanny ability to make a living bridge by clasping onto each other's limbs as they stretch across a chasm. They even monitor the flow of ant traffic across their backs, according to a 2015 study, adjusting the bridge's size and shape in real time to maximize efficiency. If too many ants join the bridge, for example, too few may be left to carry food across it.
"These ants are performing a collective computation. At the level of the entire colony, they're saying they can afford this many ants locked up in this bridge, but no more than that," says co-author Matthew Lutz, a graduate student in ecology and evolutionary biology at Princeton University, in a statement. "There's no single ant overseeing the decision; they're making that calculation as a colony."
3. Ants can also form living boats
Since fire ants live underground, floods are a nightmare scenario. But instead of scattering in a panic, they handle floods by turning the entire colony into a living raft.
One layer of ants forms the base, locking together tightly enough to form a water-tight seal that's surprisingly hard to sink, as the video above illustrates. Fire ants can assemble themselves like this in as little as 100 seconds, and if necessary, they can remain in raft formation for weeks until floodwaters subside.
4. Ants swarm like T-1000's liquid metal in 'Terminator 2'
What makes congregations of ants so sturdy yet flexible? According to a 2015 study, their secret is partly due to an ability to behave as either a solid or a liquid.
Researchers at Georgia Tech dropped thousands of fire ants into a rheometer, a machine that tests the solid- or liquid-like response of materials such as food, lotion or melted plastic. The ants showed "viscoelastic behavior," from springy resistance when pushed lightly to fluid-like flow as pressure grows. The weight of a penny, for example, prompts ants in the video above to briefly detach, sort of like water molecules. Once the penny passes through, however, they rejoin as a solid.
"If you cut a dinner roll with a knife, you're going to end up with two pieces of bread," says co-author David Hu, an engineering professor at Georgia Tech. "But if you cut through a pile of ants, they'll simply let the knife go through, then reform on the other side. They're like liquid metal - just like that scene in the 'Terminator' movie."
5. Ants talk by smell
A colony can include many millions of ants, yet queens have no intercom system to address their troops, and ants can't vocalize, anyway. So how do they coordinate all their complex collective behavior? Social media? (Antstagram, maybe?)
Ants do have language, albeit not like we do. While humans rely heavily on voices and gestures, ants make sense by making scents. Pheromones are their main mode of communication, each containing a scent message that other ants in the colony can read with their antennae. They convey a wide range of information this way, and can even combine scents or use varying amounts of pheromone to add detail.
A scout who discovers food lays down a "scent trail" to help her nestmates, for example, and as they carry pieces home, they can add more scent to reinforce the signal. As the food source dwindles, they can modify the message again by releasing less and less scent on return trips, saving other ants a fruitless hike by posting real-time updates on how much food is left. Pheromones are used for countless other purposes, too, from identifying rank and health status to sniffing out intruders.
6. Ants talk by sound, too
Ants may not have vocal chords, but that doesn't mean they're silent. Like crickets and grasshoppers, some ants are capable of "stridulation," or making noise by rubbing specialized body parts together. Ants in the genus Myrmica, for example, have a spike on their abdomen that emits sound when they pluck it with a leg.
This seems to be a call for help, according to a 2013 study, which found that other ants respond to the sound with "benevolent behaviors." Ants lack ears, but can still "hear" by sensing vibrations in the ground with their legs and antennae. (The audio clip above is an example of ant stridulation recorded by a contact microphone, which - like ants - senses vibrations through contact with solid objects.)
7. Ants' antennae can send or receive data
Antennae communication is well-known, but we still have a lot to learn about it. In March 2016, for instance, researchers from the University of Melbourne discovered that ants not only receive information through their antennae, but can use them to send outgoing signals, too. This is reportedly the first evidence of antennae serving as two-way communication devices, rather than just as receivers.
"An ant's antennae are their chief sensory organs, but until now we never knew that they could also be used to send out information," study author and Ph.D. student Qike Wang says in a press release. "Like everyone else, we assumed that antennae were just receptors, but nature can still surprise us."
8. Ants began farming before humans existed
Ants are among very few animals known to cultivate crops and livestock, skills they mastered more than 50 million years ago. (Homo sapiens, by comparison, evolved about 200,000 years ago and only began farming in the last 12,000 years.)
At least 210 ant species are fungus farmers, chewing up organic matter to fertilize crops. Most, known as lower attines, use a variety of materials like dead insects or grass, and form smallish colonies in a single "garden." Higher attines, including leafcutter ants, only use plants as fertilizer and can build massive colonies with millions of ants. Some even protect their crops with pesticides, growing bacteria that produce specialized antibiotics to suppress fungal garden parasites.
Lots of ant species tend livestock, too. Aphids are a famous example, prized by ants for the honeydew they secrete after eating sap. Chemicals on ants' feet keep aphids subdued - and can sabotage aphid wing growth to prevent escapes - but ants also reward their livestock. They herd and haul aphids to new plants, protect them from predators and precipitation, and even care for their eggs. When queen ants leave to start a new colony, they're known to carry aphid eggs with them.
9. One 'megacolony' of ants spans three continents
Every ant colony is a wonder of nature, but Argentine ants have upped the ante. The species is "unicolonial" - which means individuals can freely mix among physically separate nests - and after humans accidentally introduced it to five new continents, it set up an empire. This intercontinental "megacolony" consists of multiple regional "supercolonies," each of which is a network of allied but unconnected nests.
The largest-known supercolony, the European Main, stretches about 6,000 km (3,700 miles) from Italy to Portugal. Another, the California Large, spans more than 900 km (560 miles) in the U.S. West. Despite the vast distance between them, both are part of the same empire, scientists say, along with a third supercolony in Japan.
How do we know? Ants are territorial, and tend to fight members of their own species if they come from another colony. Yet while supercolonies include many distinct nests, ants within a supercolony treat each other like family - even if their homes are far apart. Scientists can test the size of a supercolony (or megacolony) by introducing ants of the same species from farther and farther away until they fight.
"[T]he enormous extent of this population," marvels a 2009 study on the Argentine ant megacolony, "is paralleled only by that of the human society. That's high praise, but the study also points out these ants relied on human transportation to establish their empire. And like humans, Argentine ants are notorious for wreaking havoc when they arrive in a new ecosystem: The invasive species often obliterates native ants, and without taking over the ecological services its predecessors performed.
10. Ants can lift up to 5,000 times their body weight
You may have heard that ants can carry 10, 50 or 100 times their own body weight. Any of those would be impressive, even if much of their strength is due to their small bodies. But according to a 2014 study, ants can actually lift much more than we thought: a staggering 3,400 to 5,000 times their own body weight.
"Ants are impressive mechanical systems - astounding, really," co-author and Ohio State University engineering professor Carlos Castro said in a statement. "Before we started, we made a somewhat conservative estimate that they might withstand 1,000 times their weight, and it turned out to be much more."
To assess ants' strength, researchers imaged the insects' necks with a micro-CT machine and placed them in a specially designed centrifuge. (They used Allegheny mound ants, a common U.S. species not particularly known for its strength.) While the centrifuge simulated the pressure of carrying a heavy load, the micro-CT scans revealed how the ants carry so much weight: Each part of the head-neck-chest joint has a different texture, with tiny structures that resemble bumps and hairs.
These micro-scale structures "might regulate the way the soft tissue and hard exoskeleton come together, to minimize stress and optimize mechanical function," Castro said. "They might create friction, or brace one moving part against the other."
11. Ants can help human farmers make money
People often see ants as pests. But according to a 2015 research review, certain kinds of ants can control agricultural pests as efficiently as synthetic pesticides - with the bonus of being more cost-effective and generally safer.
The review covered more than 70 studies on dozens of crop pests, mostly focusing on the effects of a tropical, tree-dwelling genus known as weaver ants. Since they live in the canopy of their host trees, near the fruit and flowers that need protection, weaver ants have a natural tendency to control pest populations in orchards.
One study found 49 percent higher yields in cashew trees guarded by weaver ants than in pesticide-treated trees. Farmers also got higher-quality cashews from trees with ants, resulting in a 71 percent higher net income. Not all crops saw such dramatic results, but studies on more than 50 pests suggested ants can protect crops including cocoa, citrus and palm oil at least as effectively as pesticides.
And horticultural help isn't limited to weaver ants. Many ants species can benefit farmers, gardeners and homeowners, despite their penchant for protecting sap-sucking aphids. Ants create and aerate soil, for instance, and healthy populations of native ants can regulate various pests like flies, fleas and roaches.
***
The pros and cons of ants vary widely by species and setting - Argentine ants are invasive pests in many places, for example, but an important native species in some South American forests. Most ants at least indirectly benefit humans in their natural habitats, with hard-to-see jobs like churning soil and spreading plant seeds. They can also help us boost our technology with biomimicry, from collective behavior that informs swarm robotics to neck joints that inspire stronger spacecraft.
Whatever the context, though, one thing is certain: It's a mistake to overlook ants.
Fascinating post! Thank you so much for sharing and warm greetings from Montreal, Canada. :)
ReplyDelete