University of British Columbia : The surprising reason bees replace their queens

What sounds like the storyline of a medieval palace drama often plays out in real-life honey bee colonies.

A once-strong ruler weakens, her supporters turn against her, and a dramatic change in leadership follows. For bees, these events are not rare. These internal takeovers carry both risks and benefits for colonies and for the agricultural systems that rely on them.

This replacement process, known as supersedure, begins when thousands of worker bees sense that their queen is no longer producing enough eggs. Acting together, they begin raising a new queen to take her place.

While this mechanism helps wild colonies adjust to shifting conditions, it can create complications in managed hives. Interruptions in egg laying, declining colony strength and reduced pollination or honey output often follow.

Researchers at the University of British Columbia have now uncovered a key reason behind these coordinated overthrows and how they unfold so precisely.

In work recently published in PNAS, the team reports that common viruses can cause a queen's ovaries to shrink. This reduces her ability to lay eggs and also lowers her production of methyl oleate, a pheromone that normally signals to workers that she is healthy. When levels of methyl oleate fall, workers detect the change and begin preparing to replace her.

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