Tongue hairs of bees are stiff and hydrophobic, new study finds

The tongue of bees, which feed on liquid food in nature, has a unique segmented surface covered with dense hairs. Since bees are able to use their tongues to adapt to the widest range of foraging environments to exploit all possible sources of liquids, the surface properties of the tongue, especially the hairs covering, would probably represent an evolutionary optimization. A new study by Chinese and German researchers shows that bee tongue hairs are stiff and hydrophobic, which is very unexpected because the structure is designed for liquid capture.

Wei et al. found that the hydrophobicity of the hairs of the tongue of bees can prevent the hairs from sticking to the soft surface of the tongue, which could significantly improve the deformability of the tongue when bees forage on various surfaces and promote their adaptability to different environments. Photo credit: Jiangkun Wei.

A bee can feast on flower nectar, sap, fruit juice or salt water.

The bee’s tongue consists of a series of ring-like segments, each bristling with 16 to 20 hairs.

It must be able to interact with a wide range of surfaces, such as narrow flower openings, coarse tree bark, irregularly shaped rotting fruit, and moist soil.

The bee’s success in exploiting these very different resources depends on the surface properties and deformability of its tongue.

Scientists had previously studied the structure and movement of hairs, but their surface properties and their relationship to overall flexibility had not received the same scrutiny.

In the new study, Sun Yat-Sen University researcher Jianing Wu and his colleagues used various forms of microscopy, along with high-speed videography and computer modeling, to study the tongue hairs of bees.

These techniques have shown that individual hairs are stiff and hydrophobic, unlike ring segments, which are soft and hydrophilic.

This difference prevents the hairs from sticking and stiffening the tongue once it begins to bend, so it can bend more to get into crevices and reach food.

The stiffness of the bristles also improves their durability, allowing the bee to use its tongue millions of times in its lifetime.

“Our findings could inspire the design of sophisticated new materials, such as flexible microstructured fiber systems for capturing and transporting viscous liquids,” the authors said.

The study appears in the journal Applied materials and ACS interfaces.

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Jiangkun Wei et al. Improved segmented bee tongue flexibility with hydrophobic tongue hairs. ACS Appl. Mater. interfaces, published online March 8, 2022; doi:10.1021/acsami.2c00431

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