How Do Ants Choose Their Queen?

10 novembre 2024

A queen ant is the main reproductive ant in a colony, meaning she’s the one responsible for laying eggs that will eventually grow into new ants. In ant colonies, which can have thousands or even millions of members, the queen is usually the largest and can live for many years—sometimes even up to 30 years! Unlike most of the other ants, known as workers, the queen is able to reproduce, which is her main job in the colony.

Big-Headed Ants Queens, Workers, and Soldiers (Credit: Nigel Main)

While worker ants are sterile females that help with food collection, nest building, and colony defense, the queen’s role is focused on making sure there are enough ants to keep the colony going.

What is the Role of the Queen Ant?

The queen ant’s role is to create a steady supply of new ants to grow and support the colony. When she starts a new colony, she lays eggs that become workers, who then handle all of the colony’s daily tasks like foraging for food, protecting the nest, and taking care of young ants. Even though the queen doesn’t actively direct or control the colony’s activities, her presence releases chemical signals (called pheromones) that help organize the colony and maintain its structure. These pheromones also help regulate when other ants become reproductive, called policing, which usually only happens when a new queen or male ants are needed for colony expansion.

From Egg to Queen: How It All Starts

An ant starts its life as an egg, and for a short period, every egg is totipotent—meaning it can develop into a worker or a queen. So, what makes one egg become a worker and another become a queen? The answer lies in a combination of environmental factors, such as nutrition, temperature, and sometimes even genetics.

Black Cornfield Ants (Lasius sp) with queen and worker cocoons

Nutrition and Diet: For many ant species, the amount and quality of food given to a developing larva is what determines if it will become a queen or a worker. Queen larvae are often fed more food and a richer diet than worker larvae. In honeybees, a similar process occurs, where larvae destined to become queens are fed a special food called royal jelly. While ants don’t feed royal jelly, they still give their future queens more protein-rich foods. This richer diet allows the queen larvae to develop into larger adults with specialized reproductive organs.
Temperature and Seasonal Changes: In some species, the temperature at which the larvae develop can influence their fate. For instance, certain types of ants are more likely to develop into queens if exposed to cooler temperatures that mimic winter. Scientists believe this adaptation helps colonies produce queens only when the season is right for them to fly out, mate, and establish new colonies.
Chemical Signals from the Queen: Queens have another powerful way to control the production of more queens: pheromones. These are chemical signals that ants use to communicate. The queen releases special pheromones that tell worker ants not to raise new queens.

Pheromones: How Queens Control Their Colony

Ants communicate primarily through pheromones. Pheromones are invisible chemical messages that tell other ants what to do, where to go, or how to respond. When it comes to controlling who becomes the next queen, pheromones play a critical role.

Certain ants, like Jumping Ants (Harpegnathos sp) will force individuals into worker states via "policing"

Inhibitory Pheromones: Queen ants release inhibitory pheromones to prevent workers from raising new queens. This helps maintain a stable colony structure.
Signals of Change: If the queen becomes old, sick, or dies, the production of these pheromones stops or slows. This triggers the workers to begin the process of rearing new queens. They might select several larvae and feed them the richer diet needed to develop them into queens. Eventually, one or more of these larvae will emerge as new queens, depending on the colony’s needs.
Policing: In ant colonies, policing refers to the behaviors workers use to maintain social order and prevent unauthorized reproduction. While the queen is usually the only ant laying eggs, some workers can lay unfertilized eggs that develop into males. However, this can disrupt the colony's organization, so worker ants engage in policing to stop it. They detect and remove these eggs, usually by eating them, thus enforcing the queen’s reproductive monopoly. This policing behavior keeps the colony stable and efficient by ensuring that resources are focused on rearing the queen's offspring, which supports the overall structure and success of the colony.

Genetic Influences: When the Queen’s DNA Decides

While environment and pheromones are the most common methods of queen selection, genetics can play a role in some ant species. For instance, in certain harvester ant species, queens are produced based on specific genetic combinations.

Certain Harvester Ants in the Pogonomyrmex barbatus and Pogonomyrmex rugosus

In these species, workers and queens belong to different genetic lineages, and only specific combinations of genes result in a queen. When a queen mates with a male of a certain genetic type, it ensures that some of her offspring will become queens while others will become workers. This genetic system is unusual and not present in most ant species, but it highlights the diverse methods ants use for caste determination.

Caste Determination in Different Ant Species

Not all ant species use the same methods for determining queens. Here’s how a few popular types differ:

1. Fire Ants (Solenopsis spp.): In fire ants, larvae that receive a high-protein diet during critical development stages have a better chance of becoming queens. Workers influence this process by selectively feeding these larvae based on cues from the current queen’s pheromones.

2. Harvester Ants (Pogonomyrmex spp.): Certain Harvester ants (Pogonomyrmex rugosus x barbatus complex) display genetic caste determination, where workers are produced through hybridization with other species, while queens are produced through "intra species mating". This fascinating mechanism allows queens to mate with males from two different lineages to produce both castes.

Weaver Ant Queen (Credit: Sunny Josef)

3. Weaver Ants (Oecophylla spp.): In weaver ants, queens emerge through environmental cues, but workers play a significant role in nurturing specific larvae to become queens. Pheromones from the queen are crucial in regulating when these larvae are raised and whether they will remain workers or become queens.

4. Honey Ants (Myrmecocystus spp.): Honey ant colonies can produce multiple queens, especially during the spring, which is mating season. The production of queens here may depend on both food abundance and the need to expand the colony’s genetic diversity by establishing new nests.

5. Furrowed Ants (Myrmica sp.): The queens of furrowed ants grow up from larvae which overwinter. Typically, the queen releases a pheromone which prevents new queens from growing up, but during the winter, these pheromones become ineffective.

Monomorium queens are very different from their workers partially due to early "differentiation" (Credit: Jonghyun Park)

6. Sneaky Ants (Monomorium sp.): The queens of sneaky ants typically are determined before they are even born. They start differentiating while in the queen based on certain hormones, such as juvenile hormone (JH).

Becoming a Queen: The Nuptial Flight

Once new queens are raised, they have one crucial task: to mate and start their colonies. Many species of ants participate in what’s known as a nuptial flight. This event occurs when virgin queens and male ants leave their home colony to mate. In the right conditions—usually warm weather after a rainstorm—the queens and males fly high into the air, where they mate.

During nuptial flights, each queen mates with several males, storing their sperm to fertilize eggs for the rest of her life. Once mating is complete, the males die, and the queens descend to the ground. If they survive the journey back, they will look for a suitable spot to start a new colony. Some queens dig directly into the ground to start a nest, while others join an existing colony.

A Final Look at Queen Selection

Ant colonies have developed an extraordinary system of caste determination that ensures their survival and adaptability. By combining environmental cues, pheromones, and genetics, they can control which larvae will become queens, keeping the colony balanced and efficient. This system highlights how highly organized and complex ant societies are, even though each ant is quite small.

In summary, while ants don’t “pick” their queens the way humans might choose a leader, their method is no less effective. Through a mix of diet, environmental signals, and intricate chemical communication, ants create the next generation of queens and ensure the colony’s continued growth and prosperity. For ants, it’s all about teamwork, and each member plays their part in this incredible, bustling society.

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