Earlier this year, Smithsonian scientists decoded the pheromones that determine whether bee daughters stay home or leave. It produced surprising clues about how simple insect societies evolve into complex communities

Bee pheromones: For some bees, growing up does not necessarily mean leaving the family nest. In flexible bee societies, daughters can either remain at home and help their mother or leave to reproduce on their own.

A new study has helped explain how those decisions are influenced by chemical signals produced by the queen.

Researchers studying the sweat bee Megalopta genalis found that queens produce pheromones that signal their reproductive capabilities and influence whether their daughters stay in the nest or leave, as per a report. The findings offer clues about how chemical communication may help organize simple insect societies and how social complexity can emerge over time.


The study was published July 28 in the journal Proceedings of the Royal Society B.

A bee society where daughters have a choice

Honeybees are known for their highly organized colonies, where individual bees have specific roles such as caring for the queen and her offspring, collecting food or guarding the nest. Chemical signals called pheromones help coordinate these roles.

But not all bees live in such rigid societies.

Megalopta genalis is a flexible social bee. Females can remain in the nest and help their mother, leave to reproduce on their own or, in some cases, take over their mother's nest.

Callum Kingwell, an evolutionary biologist at the Smithsonian Tropical Research Institute and Princeton University, pointed out that similar communication systems are still used to structure these flexible bee societies, as per a Smithsonian Magazine report.

Researchers wanted to find out whether the queen's pheromones were simply manipulating daughters into staying and working or whether they were reliable signals of the queen's reproductive ability.

Scientists identified a pheromone linked to reproduction

The researchers studied queens and their daughters on Barro Colorado Island in Panama.

Over several years, they placed hundreds of artificial nests in the bees' natural habitat. They recorded the bees' behavior and noted whether daughters stayed to work, left to reproduce on their own or took over their mother's nest.

The team also collected and analyzed chemicals found on the bees' waxy body surfaces.

They identified compounds called methylalkanes as important queen pheromones. The compounds influenced the daughters' behavior and reproductive development.

Even when the queen was not present, exposure to the methylalkanes caused daughters to display submissive behaviors typically associated with workers.

The researchers also found that the compounds slowed development of the daughters' reproductive systems and changed their levels of a hormone associated with reproduction.

The queen's pheromones appeared to be an honest signal

One of the most notable findings was the relationship between the amount of pheromone produced by a queen and her reproductive success.

Queens that produced more methylalkanes later laid more eggs and provided a greater reproductive benefit to their workers.

Higher levels of the pheromones in nests were also associated with more daughters choosing to remain at home and help their mothers.

The findings suggest that the pheromones may serve as an honest signal of the queen's reproductive ability rather than simply manipulating daughters into remaining in the nest.

Kingwell explained that producing methylalkanes requires a specific dietary protein that is also essential for reproduction, as per the Smithsonian Magazine report.

Because the same resource is needed for both pheromone production and egg-laying, the researchers said it may be difficult for queens to produce the pheromone without also having the resources needed for reproduction.

The findings offer clues about how insect societies evolve

Flexible social bees give researchers an opportunity to study why some insects cooperate while others leave to live and reproduce on their own.

Unlike honeybees, which have more rigidly defined roles, M. genalis shows a more flexible form of social behavior. Daughters can remain with their mother, leave the nest or even take over the nest.

That makes the species useful for studying the factors that influence cooperation and solitary behavior.

Bill Wcislo, an evolutionary biologist at the Smithsonian Tropical Research Institute and a co-author of the study, said “Chemical signals like these may stabilize nascent insect societies, buying time for social complexity to emerge over evolutionary time,” as quoted by Smithsonian Magazine.

The researchers said this is, to their knowledge, the first queen pheromone identified for a flexible social insect.

A lesser-known bee offers clues about social behavior

Megalopta genalis may not be as well known as honeybees, but studying the species can help researchers examine how different forms of social behavior develop.

The sweat bees are native to Central and South America, where they live in neotropical forests and nest in hollowed-out sticks.

By studying their chemical signals, reproductive behavior and relationships within the nest, researchers can explore why some daughters remain and cooperate with their mothers while others leave to reproduce independently.

Kingwell said that, “I hope that people appreciate that by studying some of the lesser well-known species of bee, we can gain insights into how evolution works and how the spectacular diversity and bee social behavior came about,” as quoted by Smithsonian Magazine.