The critical factor for determining which ants become queens or workers may be as simple as some extra insulin.

In a study published Thursday in the journal Science, researchers showed that the genes behind insulin signaling appear to play a key role in distinguishing the ants’ assignments.

In some ant species, a queen can be substantially larger and live 20 times longer than a worker, even though they are genetically identical. A number of insect species, including ants, wasps and bees, have queens that are responsible for reproduction, while a far larger number of often-sterile workers forage for food.

“We were interested in where these differences come from, how they’re regulated and how they evolved,” said Daniel Kronauer, the paper’s senior author and an evolutionary biologist at Rockefeller University in New York.