That's right — electric fields. It turns out flowers have a slight negative charge relative to the air around them. Bumblebees have a charge, too.
"When bees are flying through the air, just the friction of the air and the friction of the body parts on one another causes the bee to become positively charged," Sutton says.
It's like shuffling across a carpet in wool socks. When a positively charged bee lands on a flower, the negatively charged pollen grains naturally stick to it. The Bristol team wondered if bees were aware of this electrostatic interaction.
So, they designed an experiment — one described in this week's Science magazine. The researchers built a small arena full of fake flowers. Each flower was simple — a stalk with a small steel dish at the top. Half of the "flowers" held delicious sugar water. The other half held quinine, a substance that bees find bitter and disgusting.
When bumblebees explored this false flower patch, they moved around randomly. They chose to land on sweet flowers just about as often as bitter flowers.
But when the sweet flowers carried a small charge, the bees learned pretty quickly to choose the charged flowers. And when the electric charge was removed? They went back to their random foraging.