Supergene Shapes Fire Ant Body Size and Caste

University of Georgia researchers report that a genetic supergene influences whether red imported fire ants develop into workers or queens.

Updated on Nov. 6, 2026 in Life Sciences

Close view of red fire ant mounds on clay soil at a pine woodland edge, with ants of varying sizes moving across the dirt. — University of Georgia researchers report a supergene shapes whether red imported fire ants develop into workers or queens, with b-version carriers among the largest workers. AI Illustration. Upload story photo >

Researchers at the University of Georgia reported that a supergene influences body size and caste outcomes in red imported fire ants. Ants carrying the newer b version of the supergene were more common among the largest workers and future queens.

Why it matters

The findings link a single genetic region to differences in ant size and reproductive roles, offering insight into how social insect colonies determine who becomes a queen. Understanding these mechanisms may help explain how invasive fire ant populations organize and spread.

Experiments on about 2,500 workers per lab colony checked 1,049 worker pupae and 195 queen pupae genetically, with 191 genes more active in Bb than BB adult ants. Researchers have not yet established what gene8 does as the ants develop.

The players

University of Georgia

The public research university in Athens, Georgia, whose researchers conducted the study on red imported fire ant genetics and caste determination.

The details

Researchers collected fire ant colonies from Clarke and Oconee counties in Georgia in spring 2024 and set up small lab colonies without queens. Colonies were fed a meal containing methoprene, a chemical that acts like juvenile hormone, and pupae were weighed between 15 and 24 days later.

Around one million years ago: the newer b version of the supergene appeared.
Spring 2024: researchers collected colonies from Clarke and Oconee counties, Georgia.

The Big Picture

The study extends earlier fire ant supergene research by connecting the newer b version to body size and queen production. It adds to a body of work explaining how a single genetic region can shape the social structure of an invasive ant species.

The findings may inform future work on managing invasive fire ant populations by clarifying how colonies produce queens. Further larval experiments will be needed before any practical applications can be considered.

The takeaway

Genetic differences in a single region can shape both the size and social role of individual ants within a colony. This helps explain how colonies organize their reproductive structure.