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Researchers at the Max Planck Institute for Chemical Ecology have discovered a brood pheromone released by larvae of clonal raider ants that temporarily suppresses egg-laying in adult ants. A new study shows that larvae are not merely passive recipients of parental care; they also play an active role in shaping the reproductive dynamics of their colonies.
In the clonal raider ant (Ooceraea biroi), workers in a colony alternate between caring for larvae and laying eggs in a coordinated cycle. Researchers at the Max Planck Institute for Chemical Ecology in Jena have discovered how this cycle is controlled. The larvae emit a specific chemical signal that suppresses the fertility of adult workers. The team identified a previously unknown volatile compound produced exclusively by larvae: methyl-3-ethyl-2-hydroxy-4-methylpentanoate (MEHMP). Exposure to synthetic MEHMP drastically reduced egg-laying in adult ants—the same reaction observed in the presence of larvae. Thus, for the first time, the research team was able to chemically characterize a brood pheromone in ants. The study shows that larvae can control their parents’ reproductive behavior using chemical signals. Therefore, larvae are not merely passive recipients of parental care; they also play an active role in shaping the reproductive dynamics of their colonies.
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.
Chemical communication instead of physical contact
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.
First-ever described brood pheromone in larvae controls parental fertility
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.
A paradigm shift: Larvae as active members of ant societies
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.
Dr. Yuko Ulrich, Lise Meitner Group for Social Behavior, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, E-mail yulrich@ice.mpg.de, Tel. +49 (0)3641 57 1700
Dr. Baptiste Piqueret, Lise Meitner Group for Social Behavior, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, E-mail baptiste.piqueret@live.com
Piqueret, B.; Weissflog, J.; Tretter, S.; Zetzsche, T.; Veit, D., Bartram, S.; Halitschke, R.; Ulrich, Y. (2026) Offspring chemical control of adult reproductive transitions in a social insect. Proceedings of the National Academy of Sciences of the United States of America, 123 (15) e2526776123
doi: 10.1073/pnas.2526776123 (2026)
https://doi.org/10.1073/pnas.2526776123
https://www.ice.mpg.de/273646/social-behaviour Lise Meitner Research Group Social Behaviour
Ooceraea biroi
Source: Anna Schroll
Copyright: Max Planck Institute for Chemical Ecology
Baptiste Piqueret and Yuko Ulrich
Source: Anna Schroll
Copyright: Max Planck Institute for Chemical Ecology
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Ooceraea biroi
Source: Anna Schroll
Copyright: Max Planck Institute for Chemical Ecology
Baptiste Piqueret and Yuko Ulrich
Source: Anna Schroll
Copyright: Max Planck Institute for Chemical Ecology
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