Bumblebees can identify different flowers by the invisible patterns of scent across their surface, new research has found.
The work, led by scientists from the University of Bristol and Queen Mary University of London, revealed how bees learn the patterns and distinguish between flowers.
Flowers have different patterns of scent across their surface, with visiting bees finding that the edge of the petals may smell different to the centre.
This is in addition to patterns on flowers - such as lines pointing to the centre - that help guide bees and other pollinators towards the nectar.
Research published in the journal Proceedings of the Royal Society B shows how bumblebees can tell flowers apart by how scent is arranged on their surface.
Dr Dave Lawson, from the University of Bristol's School of Biological Sciences, said: "If you look at a flower with a microscope, you can often see that the cells that produce the flower's scent are arranged in patterns.
"By creating artificial flowers that have identical scents arranged in different patterns, we are able to show that this patterning might be a signal to a bee.
"For a flower, it's not just smelling nice that's important, but also where you put the scent in the first place."
The study found that once bees learnt a pattern of how scent was arranged on a flower, they preferred to visit unscented flowers with a similar arrangement of visual spots on their surface.
Dr Lawson described this as being the equivalent of a human putting their hand into a bag to feel the shape of an object and then picking out a picture of it.
"Being able to mentally switch between different senses is something we take for granted, but it's exciting that a small animal like a bee is also able to do something this abstract," he said.
Professor Lars Chittka, from Queen Mary's School of Biological and Chemical Sciences, said: "We already knew that bees were clever, but we were really surprised by the fact that bees could learn invisible patterns on flowers - patterns that were just made of scent.
"The scent glands on our flowers were either arranged in a circle or a cross, and bees had to figure out these patterns by using their feelers.
"But the most exciting finding was that, if these patterns are suddenly made visible by the experimenter, bees can instantly recognise the image that formerly was just an ephemeral pattern of volatiles in the air."
Dr Sean Rands, also from Bristol, added that flowers "advertise" to their pollinators by using a mixture of colour, shape, texture and smell.
The study is part of ongoing research at the University of Bristol into different ways that flowers communicate with their pollinators.