Flowers evolved a natural form of Velcro on their petals to help insects get a grip making it easier for them to pay a visit and collect nectar while carrying out that vital job of pollination.
Publishing in the journal Current Biology, Beverly Glover from Cambridge University led a team of botanists who set out to find a solution the long-standing mystery of why the flowers of many insect-pollinated plants are covered in cells shaped like minute cones or pyramids.
Glover and her team made artificial epoxy resin flowers both with and without the microscopic patterns of cone-shaped cells. They put sugar solution in the centre of the flowers and presented them to bumblebees in the laboratory giving them a choice of the smooth or rough petals.
When the petals were laid out horizontally, the bees had no particular preference for the rough or smooth petals, visiting each about half of the time. But when the petals were sloped at a steep angle, up until they were vertical, the bees preferentially visited the rough petals rather than the smooth ones.
High-speed films of the foraging bees revealed why they preferred visiting the rough petals. On the vertical smooth flowers, the bees were unable to get a grip: their feet were constantly slipping and they had to keep beating their wings to stay on the flower. Meanwhile on the rough petals, the bees quickly found a foothold and they could settle down and stop beating their wings, which saves them a lot of energy making their foraging visits far more efficient.
Previous studies have shown that bees can tell the difference between rough and smooth petals, probably by feeling them with tiny sensory hairs on the ends of their antennae. Glover and the team also tested out bees with a range of real snapdragon flowers, some with normal rough petals and a mutant strain with smooth petals. They found that when the flowers were held vertically, the bees visited the rough petals more often, presumably because they could get a better grip.
So it seems that providing insects with a safe landing pad, is one rather elegant and simple way that flowers make sure they pass on their genes to the next generation.