Picture credit: François Brassard

Ants are among the most successful creatures on Earth, thriving in ecosystems worldwide. But what drives their extraordinary social complexity and division of labour? New research published in Proceedings of the National Academy of Sciences (PNAS) uncovers a key evolutionary shift that transformed these tiny insects into ecological powerhouses.

The study, led by researchers based here at the Department of Zoology and the University of Fribourg (Switzerland), reveals that adult ants’ control over their young (larvae) was pivotal in driving the divergence of queen and worker. This divergence in size and function—known as caste dimorphism—not only enabled colony members to specialize their roles shaping the highly organized social structures seen in most ants today.

By analysing the larval characteristics, diets, and social traits of over 700 ant species, the researchers identified a surprising evolutionary pathway: ancestral ant larvae, which were ancestrally active feeders, transitioned to passive receivers of food as adults shifted to more individualized care. This transition was tied to dietary changes, notably a move away from the ancestral predation behaviour to feeding on plant-based materials. 

“Ant larvae are inherently unruly and will try to secure as much food as possible within the colony. By taking full control of larval nutrition, adult ants were able to sculpt considerably more distinct and specialized queen and worker morphology, unlocking unprecedented levels of social complexity,” said Arthur Matte, the study's lead author and a PhD student in Zoology.

"This shift in developmental control mirrors key transitions in evolution, such as the emergence of multicellular life, where individual cells lost autonomy to function as part of a larger organism," added co-author Associate Professor Adria LeBoeuf, leader of the Social Fluids Lab.

The research reveals how this greater caste specialization co-evolved with other traits of social complexity, such as larger colony sizes, worker subcastes (soldiers), and loss of worker reproductive potential. The findings support the idea that nutritional control during larval development was a critical turning point in the evolution of ants, with profound implications for understanding the dynamics of cooperative insect societies.

This groundbreaking study not only provides a new perspective on ant evolution but also underscores the importance of parental care and conflict resolution in fostering cooperative systems in nature.