Nectar is a plant’s way of bribing insects and other animals to pollinate it or protect it against herbivores. The sugar-rich fluid is indeed packed with energy, but it also contains other much-sought-after compounds.
The caffeine contained in citrus tree nectar boosts honeybees’ memories, for instance, making the insects more likely to visit similar flowers. And earlier this year several nectar components were found to reduce gut parasite load in bumblebees.
Intriguingly, a chemical component of rhododendron nectar is actually toxic to honeybees but not bumblebees, perhaps because it pays for the plants to encourage only certain, specialist pollinators.
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