How does an ant colony decide who’s fit to become a queen? In most cases, the larger a female ant grows to be, the greater chance it has to be crowned the queen of a colony. In fact, the size of ants governs the entire structure of their colonies, which are meticulously organized into multiple castes that fulfill specialized roles.
A new study published in the Proceedings of the National Academy of Sciences has found that genetics, above all else, is what often decides whether a female ant will be elevated to queen status or serve as a worker. While both environmental conditions and genes play a role in ant size, genetic variation helps a few female ants stand out from the rest, bestowing them with queen-like traits that emerge early.
The Anatomy of an Ant Colony
Ant colonies generally consist of three types of ants: males (drones), non-reproductive females, and a queen.
The wingless, non-reproductive females are almost always smaller than the queen. They’re the ones doing all of the hard work around the colony; workers spend their busy days scavenging for food, caring for the queen and larvae, and keeping the colony clean. Brawnier females with powerful mandibles act as bodyguards, protecting the colony from intruders.
Winged males, meanwhile, have one primary duty: mating with the queen. And since colonies are ever-expanding, males and virgin queens-to-be will leave their colonies and embark on nuptial flight. During this yearly event, virgin queens attract several males to mate with midair and then land and lay eggs, thereby starting a new colony. The males don’t get to stay around for long — they die quickly after reproducing with a queen.
Read More: Crazy Ants Lead the Way for Swarm Intelligence, Helping Colonies Plan Complex Tasks
The Reign of Ant Queens
The researchers involved with the new study set out to understand why certain female ants become queens while others don’t, which could also offer insight into the organization of ant castes.
"One of our goals is to understand how an insect society functions," said author Daniel Kronauer, a professor of evolution at Rockefeller University, in a statement. "Studying how individuals differentiate in a colony can inform our understanding of the types of caste systems, from queens to workers to soldiers, that can evolve in the thousands of ant species out there."
Environmental factors, such as food availability and temperature, have been considered crucial elements that determine an ant’s body size. But what truly matters is genetics. Prior research has shown that when genetically identical ant larvae were raised with less food, they would become smaller and miss out on developing queen-like traits. However, if the larvae managed to reach a certain size despite the lack of food, they would still develop queen-like traits.
Genes Fit for a Queen
To determine the importance of genes in body size and caste organization, the researchers examined clonal raider ants. Although these ants don’t have conventional queens, they have individuals known as intercastes that develop traits similar to those of queens. The reason these ants were used is that their genotypes can easily be controlled.
The researchers tested genetically different larvae of these ants under similar environmental conditions. They found that not only do their genes influence size, but they also mandate when an ant will develop queen-like traits.
Ants from one genetic line, which the researchers labeled “M,” consistently grew to smaller average body sizes than those from another line, labeled “A,” even when raised under the same conditions. However, for any given body size, line M ants were more likely to develop queen-like traits.
What this means is that some ant genotypes start to express queen-like traits at smaller sizes.
"If some environmental factor affects caste, it will affect size too,” said author Patrick Piekarski, now a postdoctoral researcher in the Kronauer lab. “It can’t induce change in one and not the other. As far as we can tell, no matter which environmental variable you manipulate, the relationship between ant body size and caste remains unchanged and is instead genetically encoded."
The researchers believe that their findings have important implications for understanding ant colonies as superorganisms, which contain genetically identical individuals that perform different roles, just like cells in a tissue.
Read More: Ants Do Poop and They Even Use Toilets to Fertilize Their Own Gardens
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Proceedings of the National Academy of Sciences. Static allometries of caste-associated traits vary with genotype but not environment in the clonal raider ant
Natural History Museum. Flying ant day: When winged ants take their nuptial flight
Journal of Experimental Biology. Caste development and evolution in ants: it's all about size
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine
