Bumblebees are trained to go to iridescent surfaces for sugary rewards
Bees and plants talk to each other in a colourful language that humans cannot see or hear, researchers claim.
Scientists at Cambridge University said flower petals use iridescence, which causes differences in colour perception, to attract pollinators.
It was already known that insects, birds, fish and reptiles use iridescence for species recognition and mate selection.
Research revealed plants use it to make themselves attractive to bees.
The university team identified iridescence in hibiscus and tulip flowers and showed that bumblebees could separate iridescence and colour.
In laboratory experiments, bumblebees were taught to recognise that iridescent discs containing yellow, blue or violet pigments offered a sugary reward.
They learned to fly to these discs and avoid others with the same pigments which were not iridescent.
The findings were reported in the journal Science.
Most petal iridescence is at the ultraviolet end of the light spectrum which is visible to insects but not to humans.
Dr Beverley Glover, from Cambridge University, who led the study, said: "Our initial survey of plants suggests that iridescence may be very widespread.
"From gardening to agriculture, flowers and their pollinators play an enormously important role in our daily lives.
"It is intriguing to realise that they are signalling to each other with flashing multi-colours that we simply can't see."