The Lise Meitner Group Social Behavior , led by Yuko Ulrich, is conducting research on a special ant species: the clonal raider ant Ooceraea biroi . This ant species does not have queens. Instead, all workers are capable of reproducing asexually without mating, a process known as parthenogenesis. In most social insect species, however, the queens lay the eggs while the workers care for the brood. These roles are clearly defined, with no alternation between egg-laying and brood care. In contrast, all females in Ooceraea biroi are capable of both reproduction and brood care, and the colonies alternate between these two phases. "We wanted to know which factors regulate the reproductive cycle — that is, the alternation between egg-laying and caring for offspring — in our ant system," explains lead author Baptiste Piqueret.
Previous studies have shown that the presence of larvae is crucial for regulating the egg-laying behavior of adult ants. However, it was unclear whether the larvae secured parental care through physical contact, behavior, or chemical signals. "Since ants have a highly developed sense of smell, we suspected that the larvae release a chemical signal that inhibits egg-laying," says Yuko Ulrich.
These considerations motivated the research team to search for a specific chemical signal emitted by the larvae. To accomplish this, the researchers collected volatile chemical compounds released during the ants' various developmental stages—from egg to larva to pupa to adult ant. They identified a compound emitted exclusively by the larvae, methyl-3-ethyl-2-hydroxy-4-methylpentanoate (MEHMP). "The biggest technical challenge was detecting this compound in extremely small quantities and synthesizing it in a way that allowed us to test it experimentally and ultimately confirm its role as a pheromone," says Yuko Ulrich.
To eliminate the influence of physical contact, scientists designed an experimental setup that allowed ants to smell larvae without touching them. They also exposed the ants to synthetic MEHMP in behavioral experiments and compared the results with those of several control experiments to rule out other causes of the observed behavior. The results of these experiments clearly showed that the odor signal of the larvae was sufficient to suppress further egg-laying in adult ants, even when the odor was synthetic MEHMP and no larvae were present.
"Ants go through various immature brood stages, including eggs and larvae. Due to the significant differences in their physiology, we initially assumed that we would find dozens of compounds in each brood stage and thus have several candidates for inhibiting fertility in adult ants. However, in our investigations, we found only one candidate,” Baptiste Piqueret summarizes the surprising result.
Scientists also have an explanation for why ant larvae rely more on chemical messenger molecules than tactile signals. This is linked to the lifestyle of clonal raider ants. Although their reproductive phases alternate between caring for the brood and laying eggs, a division of labor still exists: some workers care for the larvae while others forage for food. Nevertheless, the reproductive cycle remains synchronized among all workers in the colony. Thus, the pheromone signal also reaches workers that do not come into contact with the larvae.
MEHMP is the first described brood pheromone in ants. This challenges previous assumptions about the role of larvae in ant societies. "Larvae and brood in general have often been described as passive members of ant societies. However, this first ant brood pheromone suggests that larvae can play a much more active role in an ant society than was previously thought," says Baptiste Piqueret. In colonies of clonal raider ants, MEHMP helps synchronize brood care and reproduction. Since only the larvae produce this pheromone, the adults' fertility is no longer inhibited after pupation. The ants reproduce again by laying new eggs. As soon as the eggs develop into larvae, the ants stop laying eggs and return to caring for the brood.
The study raises new questions for Yuko Ulrich and her team. For instance, they want to determine how adult ants perceive the newly discovered pheromone, how the odor is processed in their brains, and how odor perception controls the hormonal regulation of reproduction. They also want to investigate whether similar pheromones exist in other ant species that are found exclusively in larvae.
Proceedings of the National Academy of Sciences
Experimental study
Animals
Offspring chemical control of adult reproductive transitions in a social insect
8-Apr-2026