Caffeine occurs naturally in the nectar of coffee plants and citrus trees, in concentrations too low to turn the taste bitter but high enough to lure bees—which remember the source and go back for more.
Newcastle University researchers taught hundreds of the insects to react to certain scent triggers (like Pavlov and his dogs), then analyzed their behavior.
“If they’re just being trained with sucrose, they don’t remember the scent very well the next day,” says lead researcher Geraldine Wright. “When we spiked the reward with the amount of caffeine found in nectar, they were able to remember” the drug-laced scent for up to three days.
Some plants ward off hungry herbivores with toxins like caffeine or nicotine, but in this case, “a plant is using one of these compounds to manipulate the animals to its own benefit.”
The situation appears to be a win-win: The flowers retain a faithful pollinator, and the bees know where they can find their fix—kind of like a Starbucks for honeybees.