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Bumblebees are attracted to the humidity of flowers

Flowers possess an invisible feature that attracts bumblebees, according to a new study led by the University of Bristol. The experts report that bumblebees may use the humidity of a flower to tell them about the presence of nectar.

The researchers determined that bumblebees are able to accurately detect different levels of dampness next to the surface of the flower.

“Our study shows that bumblebees not only use this sensory information to make choices about how they behave, but are also capable of learning to distinguish between humidity patterns in a similar way to how they learn to recognize the color or smell of a flower,” said study co-author Professor Natalie Hempel de Ibarra.

To investigate, the researchers designed artificial flowers with levels of humidity similar to those of flowering plants.

“Bumblebees showed a spontaneous preference for flowers which produced higher floral humidity. Furthermore, learning experiments showed that bumblebees are able to use differences in floral humidity to distinguish between rewarding and non rewarding flowers,” explained the study authors.

“Our results indicate that bumblebees are sensitive to different levels of floral humidity. In this way floral humidity can add to the information provided by flowers and could impact pollinator behaviour more significantly than previously thought.”

According to study lead author Dr. Michael Harrap, it is known that different species of plants produce flowers that have distinct patterns of humidity, which differ from the surrounding air.

“Knowing that bees might use these patterns to help them find food shows that flowers have evolved a huge variety of different ways of attracting pollinators, that make use of all the pollinators’ senses.”

“If humidity patterns are important for attracting pollinators, they are likely to be one of several different signals (such as colour, scent and pattern) that a flower is using at the same time, and could help the bee to identify and handle the flower more efficiently,” said study co-author Dr. Sean Rands.

“The effectiveness of humidity patterns may depend upon the humidity of the environment around the flower; climate change may affect this environmental humidity, which in turn could have a negative effect on a visiting bee because the effectiveness of the humidity pattern will be altered.”

The study is published in the Journal of Experimental Biology.

By Chrissy Sexton, Staff Writer

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