If considering sheer size, perhaps you  immediately thought of the ocean - and the  

largest animal that's ever lived - the blue whale.  Or perhaps thinking of strength and ferocity,  

you imagined lush forests full of fearsome big  cats. Or maybe, quite sensibly, you thought of  

us - human beings- the most intelligent, and one  of the most widespread creatures on the planet.  

But if you were to walk down the sidewalk, or lean  against a tree, the first animal that you would  

likely encounter is something small - ants. Their  total population is around ten thousand trillion,  

and when combined their total weight would be  about the same as the weight of all human beings.  

in biomass and in impact on ecosystems,  these small animals are arguably the most  

successful creatures to have ever lived. Ants have colonized almost every landmass on  

earth. Their presence is so significant that they  have directed the evolution of countless other  

plant and animal species. Aggressive, warlike,  but also cooperative, altruistic - ants living  

in colonies exhibit some of the most complex  behaviors of all insects. And the colony is the  

only thing that matters in the lives of ants.  Their loyalty to it is absolute. And in their  

service to it, they exhibit some of the most  complex social behavior in the animal kingdom,  

giving rise to their nearly complete  ecological conquest of the earth.  

How do ant societies work, and what is it about  the colony that has made ants so successful?  

Is it as simple as “strength in numbers?”  Or is it something more profound?  

Even though insects were among the first  animals to colonize land, cooperative insect  

societies are a relatively recent development. The first insects emerged around 400 million  

years ago - but ants didn't emerge until  much later, around 100 million years ago.  

They lived amongst the dinosaurs, and for a long  time did not rule the landscape. This was the  

era of the giant dragonflies, cockroaches, and  termites. It wasn't until 60 million years ago  

that they became the dominant insects. And since  then, they have truly flourished. Today there are  

around 16,000 different species of ant, and they  are found on every continent except Antarctica.  

The competitive edge that allowed ants  to become a world-dominant group is their  

highly developed colonial existence  and specialized social structure.  

Ant societies are broken up into two castes: a  non-reproductive worker caste, and a reproductive  

royal caste. The queen is the only reproducing  female of the entire colony, and the colony  

exists to serve her, and her alone. The birth  of a colony begins with the birth of a queen.  

The life of a queen begins when its mother queen  lays a special kind of egg, different from the  

millions of regular worker eggs the queen ant  will lay in her lifetime. These special eggs  

are laid when the colony passes a certain size -  and when they hatch, they produce ants that are  

larger than regular workers and have wings. These  are the reproductive males and young queens.  

During what is called a nuptial flight  these winged ants take to the air and  

mate with each other, after which the males  die and the females drop to the ground,  

scrape off their wings and begin to search for  a place to dig their nest. Few get far in this  

journey. Predators snag most of these young  queens before they can establish themselves.  

Only around 1 in 500 new queens has a chance  at success. But those that do succeed become  

the single egg-laying queen of their new colony. Over the course of her life, a queen ant can lay  

up to 300 million eggs, depending on the species  of ant. And the vast majority of these eggs  

hatch into dedicated worker ants - female ants  whose lives are devoted to the queen's welfare  

and reproductive activity. At any given time,  there are millions of worker ants maintaining  

the colony. There can be many different types,  and many different sizes of workers even within  

a single colony. Some care for larvae, others  excavate tunnels, others build amazing structures,  

while others leave the nest and search for  food, or go to war with neighboring colonies.  

And surprisingly, it is the ant workers themselves  who ultimately decide the fate of the young,  

choosing which worker caste they  will develop into. Larvae develop  

into different types of workers based  largely on the nutrition they receive.  

Those fed more insects than seeds are  more likely to become larger individuals.

For leaf cutter ants, the polymorphism  that exists among the workers is extreme.  

The largest workers, called soldiers, defend  the colony, while the medium sized workers  

collect leaves, excavate tunnels, or collect  garbage, and the smallest workers raise the  

young and cultivate and farm fungus - the  only food source for the whole colony.  

The workers toil away in a flawless synchrony  - in a flow that looks chaotic to our eyes,  

but is in fact based on a  complex system of communication,  

a chemical and physical language invisible  to us, but binds these societies together.  

For years, scientists knew that ants must  have some way to talk to each other in order  

to organize their intricate societies.  But ants have poor vision and hearing,  

so scientists knew that ant communication must  work in a fundamentally different way to ours.  

It was a mystery for years, but in 1962 leading  entomologist EO Wilson began to crack the code  

of ant communication. He started with the  question of how ants tell other members of  

the colony the location of a new food source. He  noticed that ants often tap their abdomen to the  

ground when travelling, so wondered if they  were leaving some sort of chemical trail.  

He began painstakingly dissecting fire ant  abdomens, crushing each of the organs with  

an applicator stick. He would then spread  the ant juice on a piece of paper in front  

of other fire ants, to see if they would react.  As he worked through each of the known organs,  

the ants showed no interest. But then he stumbled  upon an organ that had never been studied  

before - something called Dufour's gland. When he  crushed this gland and spread it across the paper,  

the ants went wild. They followed the  trail immediately and completely.  

Over time, scientists have discovered over 20  different pheromones that ants use to communicate.  

And by combining different signals, ants  have created a complex pheromonal language.  

African weaver ants, in particular, have the most  sophisticated pheromone communication system ever  

studied in animals. Some of their thoughts are  expressed by spreading pheromones on the ground,  

like previously mentioned,  combined with physical gestures.  

When a worker wishes to say 'follow me I have  found some food' she deposits a trail from the  

rectal gland, while running from the food back  to the nest. When she encounters other workers,  

she waves her head and touches the other ant  with her two antennae. Or when a worker wishes  

to raise the alarm about an enemy, she lays  short looping trails around the intruder with  

secretions from the sternal gland. Other signals are sent through the  

air. When an African weaver ant worker  encounters an enemy in her own territory,  

she releases a mixture of four chemicals that  not only convey a message but elicit a response  

from all other workers in her vicinity. The first tells the other ants to 'be alert'.  

The next one tells them to search for the  trouble. The next one tells them to come  

closer and bite anything in their path, and the  final compound tells them to go nuts and attack.  

Scientists believe that the combination of  these signals very closely resembles syntax  

that we see in human language. A main reason ants  are so successful in the world then, is the same  

reason that humans are. Like us, communication  gives ants the amazing capacity to cooperate.  

Of all ants, weaver ants are among the most  impressive. They dominate the forests in  

Africa and Australia, in large part due to their  complex and efficient chemical communication.  

But perhaps more remarkable than their  ability to communicate so effectively,  

is what they can achieve with it. Weaver  ants are a species of ant that do not live  

in or on the ground, but in the trees. And  to keep their huge populations safe there,  

they construct their own housing. They weave  branches and leaves together to create an  

architectural feat, full of a network of different  rooms complete with roofs, walls, and floors.  

To begin the process, a single ant searches for  a nice, bendy looking leaf. It will pull on the  

edges, testing to see if the leaf will curl.  If the ant has some measure of success, other  

ants will be attracted to the endeavor, and begin  pulling the edge as well. As the leaf bends more,  

more workers arrive. They line up in precise rows,  gripping the edge, pulling it towards another  

leaf. If the gap is too large for a single row of  ants to seal, they perform an impressive acrobatic  

tactic: they chain their bodies together to form  a bridge. Workers climb down the bodies of others,  

until the chain can reach the other leaf edge, up  to 10 workers long. Once the leaf edges are within  

reach, the workers move into position to seal the  leaves together. But what looks like glue on the  

finished structure is something more surprising. Once the bent leaves are ready to be sealed,  

the workers will collect larvae who are  in their final stages of development,  

and use their threads of silk to bind the leaves  together. Holding the larvae in their mandibles,  

the workers move the larvae back and forth across  the leaf edges - using their babies like a hot  

glue gun. The larvae seem okay with this, as they  respond to this motion by exuding thousands of  

threads of silk. This silk becomes a sheet between  the edges, and works as a powerful adhesive.  

Structures like this speak to ants capacity  to organize their labor effectively, millions  

of individuals combining their abilities into  something much greater. It's easy to assume, then,  

that their effectiveness comes down to a strength  in numbers, along with the communication to  

orchestrate the work. But this can't account for  all of their behavior, and all of their success.  

There is something more unifying in the world of  the ants. And the individual ant's cooperation  

with one another is so profound, that it makes  scientists rethink the idea of individuality.  

The power of a group is evident - with more ants  working together, they can find food more quickly,  

build more impressive structures, and  defend against enemies more effectively.  

And working together is common in nature -  birds in flocks, or bison in herds live longer  

when they live in groups. But in cooperative  animal groups like these, individuals still  

look out for their personal interests.  For them it's not just about the group.  

But this is not the case for ants. Worker ants  die young, and usually don't create offspring.  

Their existence is sacrificial. They have no self  interest. Certain ants have been found to suffer a  

death rate of 6% per hour when outside the nest,  due to fighting with neighboring colonies. On  

average each forager survives for only a week. But  during that time, she manages to collect 20 times  

her own body weight in food for the colony - all  to support the group, and ultimately, the queen.  

This unwavering loyalty to the queen,  and the self sacrifice to her cause,  

becomes more evident when a queen dies. Logic  would assume that when the queen dies the workers  

would raise another queen to replace her. But this  is not at all what the workers do. In most cases,  

the colony fails to produce a royal successor,  and it declines until the last worker dies. They  

simply do nothing until there is no one left. This level of altruism and self sacrifice is so  

rare in the animal kingdom, that it has  made scientists rethink what it means  

to be an individual. If ant individuals in a  colony are not competing against each other,  

if they are bound tightly by communication and a  caste-division of labor, if they cannot survive  

out of the colony for very long - does the  concept of the individual break down?  

The idea of the superorganism is one that has  been debated for decades. With ants, it's the  

idea that the colony is the organism, where the  queen is the reproductive organ, the workers the  

supporting brain, heart, and gut. The exchange of  food among the workers is like the circulation of  

blood. [6] The most advanced ant societies, like  weaver ants, driver ants, or leafcutter ants,  

fall into this category, where their workers  do not compete amongst themselves at all,  

and do not reproduce outside of royalty. This capacity of the colony to act like a single  

superorganism has made scientists reconsider  evolutionary theory as a whole. In the 1960s  

and 70s, the conventional way of thinking  about evolution was centered around genes,  

and genes alone. Largely popularized by Dawkin's  book The Selfish gene, it follows that the more  

two individuals are genetically related, the more  sense it makes for them to behave selflessly with  

each other - that all altruistic group behavior  comes down to each individual's competitive desire  

to improve chances of their kin's survival. But some ant biologists, like EO Wilson,  

believed that this couldn't be the whole story.  Instincts from social species like ants go far  

beyond the urge to protect their immediate kin.  The group must also have a role in evolution,  

whether or not the group members are related  to each other. And this idea gave rise to the  

theory of multi-level evolution, or group  selection, where natural selection acts  

at the level of the group, instead of at the  more conventional level of the individual.  

The way ant societies function, in their daily  lives and within evolution, has entranced us as  

humans for decades. They have created heated  debates among the world's top scientists,  

and been the focus of every kid's backyard  curiosity. Their world operates in ways our  

brains can barely conceive - with chemical  signals painted on the ground, instincts that  

drive them to fatal endeavors - and yet, their  sociality, cooperation, and complexity in many  

ways mirrors our own. Studying ants will continue  to reveal answers about the nature of evolution,  

and in turn, will reveal answers about our  own society, and our own individuality.  

Studying the animal kingdom gives insight into  our world, and brings researchers on all sorts  

of journeys - both intellectual and physical. Some  of the research about ants happens in the field,  

in the steamy tropics or the  frigid parts of northern Finland.  

And some of it is done in the lab, with  complex apparatuses engineered to study  

ant's chemical trails or their inclination to  go to war with each other. Hearing about what  

it takes to carry out research like this is often  just as interesting as the science itself. I love  

hearing the human stories behind the science -  and this is why we decided to start a podcast.  

Modulus - hosted by me, and Brian from  Real Engineering, is a podcast about the