Flowers have evolved a form of “natural Velcro” that helps bees cling on when collecting nectar, research has shown.

The petals of most flowers are lined with microscopic conical cells but scientists had never been quite sure what they were for. Now British researchers have demonstrated that they help bees get a grip and so make it easier for them to feed.

Without the cells, bees are left “scrabbling and sliding” like mountaineers on an icy cliff, said Beverley Glover, of the University of Cambridge. “I have been studying these cells for many years and had always wondered whether this simple explanation could be the reason for their presence,” said Dr Glover, one of the authors of a paper published in the journal Current Biology.

“For bees to maintain their balance and hold on to a flower is no easy task, especially in windy or wet conditions. Evolution has come up with the simple solution of equipping flowers with a Velcro-like surface that bees can get a grip on.”

For plants that rely on insects to spread their pollen, anything that attracts pollinating insects would be an evolutionary advantage.

Dr Glover’s team created artificial, lollipop-shaped flowers from epoxy resin, half with replicas of the spiky cells and half with flat surfaces. When the “petals” were horizontal, they found that bees were attracted equally to the two types.

But the bees’ preference for the spiky surfaces increased as the petals were angled more steeply, and when they were vertical, bees chose them more than 60 per cent of the time.

The effect was even more pronounced with real flowers. The team compared normal snapdragons, which have the cells, with a similar variety that lacked them. Again they found no difference when the flowers were horizontal — but when they were vertical the bees preferred the flowers with the “Velcro” three quarters of the time.

High-speed photography of the experiment confirmed that the bees were struggling on the smooth surfaces. “After landing, the bee repeatedly attempted to find footholds, scrabbling particularly with the middle pair of legs,” the authors wrote.

“These attempts at landing on a flat-celled epoxy cast were always unsuccessful, with the feet continually slipping. However, in all recorded incidents the bees were able to find grip on the conical cells.” They were then able to stop beating their wings and feed while at rest, so using up less energy.

Dr Glover said she thought that all pollinators that land on flowers, including butterflies, bats and beetles, would prefer flowers with the spiky cells.

“However, flowers that are primarily pollinated by hovering animals — moths and hummingbirds, for instance — might be expected not to bother with these grip-providing surfaces.”

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