The honeybee tongue, foraging liquid food in nature, has a unique segmented surface covered with dense hairs. Since honeybees are capable of using their tongue to adapt to possibly the broadest range of feeding environments to exploit every possible source of liquids, the surface properties of the tongue, especially the covering hairs, would likely represent an evolutionary optimization. A new study by researchers from China and Germany shows that honeybee tongue hairs are stiff and hydrophobic, the latter of which is highly unexpected as the structure is designed for liquid capturing.
A honeybee can feast on flower nectar, sap, fruit juice or salt water.
The bee tongue consists of a series of ring-like segments, each bristling with 16 to 20 hairs.
It must be able to interact with a broad spectrum of surfaces, such as narrow flower openings, coarse tree bark, irregularly shaped rotten fruit and damp 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 motion of the hairs, but their surface properties and relationship to overall flexibility hadn’t received the same scrutiny.
In the new study, Sun Yat-Sen University researcher Jianing Wu and colleagues used various forms of microscopy, along with high-speed videography and computational modeling, to study honeybee tongue hairs.
These techniques showed that the individual hairs are stiff and hydrophobic, unlike the ring segments, which are soft and hydrophilic.
This difference prevents the hairs from sticking to and stiffening the tongue once it starts bending, so it can bend further to get into crevices and reach food.
The stiffness of the hairs also enhances their durability, enabling the bee to use its tongue millions of times during its lifetime.
“Our findings could inspire the design of sophisticated new materials, such as flexible microstructured fiber systems to capture and transport viscous liquids,” the authors said.
The study appears in the journal ACS Applied Materials & Interfaces.
Jiangkun Wei et al. Enhanced Flexibility of the Segmented Honey Bee Tongue with Hydrophobic Tongue Hairs. ACS Appl. Mater. Interfaces, published online March 8, 2022; doi: 10.1021/acsami.2c00431
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