Etya Amsalem, Penn State University - The Workers Behind the Throne — The Academic Minute

Why do some bumblebee larvae become queens while others do not?

Etya Amsalem, associate professor of entomology at Penn State University, looks for the answer.

Faculty Bio:

Etya Amsalem is an Associate Professor of Entomology at Penn State University. She earned her M.Sc. and Ph.D. in Zoology from Tel Aviv University, Israel, and completed postdoctoral training at Penn State University and the University of Haifa, focusing on chemical communication, insect genomics, and bee health. Her research examines the evolution and mechanisms of social behavior in insects, integrating approaches from chemical ecology, evolutionary biology, functional genomics, behavior, and physiology.

Transcript:

When we think about a bee colony, we often imagine a queen ruling her kingdom. But in some social insects, the colony functions less like a monarchy and more like a self-organizing society.

A defining feature of social insects is the division of labor between females. Queens and workers often share the same DNA, yet develop into individuals with very different roles. Queens are large, long-lived, and reproductive, whereas workers are smaller and typically nonreproductive.

But what determines which larvae become queens?

My colleagues and I investigated this question in bumblebees, seasonal social insects that are also vital pollinators. A single queen starts a colony in the spring and produces hundreds of workers that rear her offspring. Later in the season, workers begin laying their own eggs, while the colony starts producing new queens.

To understand how the same DNA produces both workers and queens, we manipulated juvenile hormone levels in workers and larvae and tracked the movement the labeled hormone. Juvenile hormone regulates reproduction and development across insects, but it was unclear who controls caste development and how these signals reach larvae.

Workers treated with juvenile hormone produced larger offspring and more queens. In contrast, treating larvae directly did not produce queens and often caused workers to eliminate them. We also found that larvae respond only during a brief developmental window. Most importantly, we discovered that workers transfer juvenile hormone to larvae during feeding, providing direct evidence that workers regulate queen development through hormone transfer.

These findings reveal a bottom-up rather than top-down system. As workers mature, their hormone levels rise, increasing the amount transferred to larvae. Collectively, these interactions determine which larvae become the next generation of queens, showing that the colony’s future is shaped not by the queen alone, but by the workers themselves.

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