Queen bees more likely to be executed by their workers if they mate with multiple males, research shows

Yohannes Lowe
Proportion of diploid males in grey, and female workers in colour - Ayrton Vollet

Queen bees are at a greater risk of execution from their workers if they mate with more than one male, new research has found.

Queen stingless bees normally only mate with one male, who is the father of the colony's workers, in order to lower the effect of producing infertile offspring, known as 'diploid males'.

Diploid males share one of the queen's two alleles- different versions of the same gene. They emerge from their cells around a month after the eggs have hatched.

It is at this stage that worker bees can execute a queen, as they sense that her offspring are defective and serve no useful reproductive function.

For every diploid male produced, it means there is one less worker bee in the colony.

The experiment, carried out by the University of Sussex and the University of Sao Paulo, compared the fate of queens in different hives in Brazil.

Scientists monitored colonies which produced 50% diploid males- when the queen mated with one male who shared a sex allele with her.

They also monitored other colonies which produced 25% diploid males- when the queen mated with two males, but only shared a sex allele with one.

Queen stingless bees normally only mate with one male Credit: Ayrton Vollet

Because the queen was just as likely to be executed in both colonies, it showed that by mating with two males the queen actually doubled her chance of being executed.

Francis Ratnieks, Professor of Apiculture (beekeeping) at the University of Sussex, said: “By studying test colonies, we found that queen stingless bees will have an increased chance of being executed by the workers in their colony if they mate with two males instead of the one male they normally mate with.

“The reasons for this are fairly complex, but in short, it is due to the genetics of sex determination in bees and the risk of what is known as 'matched mating'.”

“The project tests a long standing idea of mine that if stingless bee queens mate with two males instead of one that it will increase their chances of being executed. It was quite satisfying that an idea that was thirty years old could finally be tested, especially when the hypothesis was found to be correct,” Prof Ratneiks added.

The study, published in the American Naturalist, helps biologists to understand why some species mate with multiple males, while others only remain with one.

The Honey Bee, which can be found in parts of the UK, is a species known for its queens mating with between ten and twenty males.

Queen stingless bees are closely related to honeybees and bumblebees, but are found in tropical climates such as Brazil.