They say love is blind - and for queen honeybees that is literally true

A queen honeybee at the centre of the hive. Credit: Barbara Baer-Imhoff/UCR

They say love is blind ... and for a honeybee queen this is certainly true.

Males inject toxins into the queen while mating that causes temporary loss of sight, according to a new study.

The result means that as she is unable to take flight (if she can't see, she can't fly) amorous males that do get the chance to mate get longer to do so and enhance the chances of their genes getting passed on.

All sexual activity occurs during a brief early period in a honeybee's life, during which males die and queens can live for many years without ever mating again.

Boris Baer, a professor of entomology at the University of California Riverside, said male bees develop vision-impairing toxins to maximise the one fleeting opportunity they may ever get to father offspring.

Males bees produce hundreds of different toxins for specific 'missions'. Credit: PA

"The male bees want to ensure their genes are among those that get passed on by discouraging the queen from mating with additional males," said Baer, senior author of the study published today in the journal eLife.

"She can't fly if she can't see properly."

Earlier work by Baer's team also discovered honeybee seminal fluid toxins that kill the sperm of rivals.

All honeybees make these proteins, though some may make more of it than others.

A queen bee is set with a yellow dot on its body. Credit: PA

During early projects, Baer noticed that if bumblebee queens were injected only with the fluid and not the sperm during insemination, the queens stopped mating and became increasingly aggressive toward males. He wanted to understand why.

Roughly 10 years ago, Baer and his international team began analysing which proteins could be found in honeybees' fluids.

"We found at least 300 of these 'James Bonds,' little secret agents with specific missions," he said.

In tests, Baer's team presented inseminated queens with a flickering light, and measured her response to it via tiny electrodes in her brain.

The vision and corresponding flight-impairing effects kick in within hours, but it is likely reversible in the long term as queens do tend to fly successfully later in life when they establish new colonies.

Bees are a critical part of the food chain but are declining in numbers. Credit: PA

A molecular understanding of honeybee mating habits could eventually be used to improve breeding programmes and help insects that pollinate many of the foods we eat.

"More than a third of what we eat depends on bee pollination, and we've taken bees' services for granted for a very long time," Baer said.

"However, bees have experienced massive die-offs in the last two decades. Anything we can do to help improve their numbers will benefit humans, too."