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Bumblebees that get a caffeine boost are better able to remember the odours of specific flowers, helping them to forage for them in future.

The caffeine appears to enhance bees’ learning and memory skills, even if there is no caffeine in the flowers they ultimately choose. Previous research has shown that bees have a preference for flowers with naturally caffeinated nectar, such as coffee and citrus plants, but it was unclear whether the caffeine boosted their performance or if they actually craved the caffeine itself.

and Jan-Hendrik Dudenhöffer at the University of Greenwich, UK, crafted a synthetic odour of strawberry flowers, which aren’t naturally caffeinated, and provided it along with sugar water to feed to laboratory bees in their nests. Then they added a small, tasteless dose of caffeine to the nectar in about half those nests. The researchers also fed unscented sugar water to a control group of bees.

Starting the next day, Dudenhöffer let the bees explore an area containing eight flower-like robots which would distribute synthetic nectar when the bees landed on them, and then refill themselves. Half the robots smelled like strawberry flowers, and the other half smelled like linalool, an odour found in many kinds of flowers, but not strawberry plants. All the robots provided sweet nectar as a treat, but none of them contained caffeine.

Bees that had fed on neutral sugar water in their nests showed no preference for any of the flower robots, visiting the strawberry-smelling ones about half the time. Those that had been fed a caffeine-free strawberry flower nectar selected the strawberry-smelling robots more frequently – about 60 per cent of the time.

The bees that had had caffeine in their strawberry nectar, however, showed a strong preference for the strawberry-scented robots, visiting them 70 per cent of the time, says Arnold. In addition, they learned to gradually get faster as they foraged – even more so than the bees that had not had caffeine.

“We anticipate that the caffeine-odour-sugar exposure the bees had in the nest helped them form a strong memory that the synthetic strawberry flower odour was ‘good,’ and they went seeking the odour,” she says. “It seems they remembered that good experience more strongly and for longer.”

Practically speaking, this suggests bees could learn to associate the specific smells of a farmer’s crops with a sweet taste of it in their nests, topped up with a touch of caffeine. Commercially prepared bees could be “ready primed to seek out the crop’s flowers” as opposed to weeds and wildflowers, says Arnold.

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