School of Agricultural, Forest and Environmental Sciences, Clemson University, Clemson, SC 29634, USA.
J R Soc Interface. 2013 Jun 12;10(85):20130336. doi: 10.1098/rsif.2013.0336. Print 2013 Aug 6.
Mouthparts of fluid-feeding insects have unique material properties with no human-engineered analogue: the feeding devices acquire sticky and viscous liquids while remaining clean. We discovered that the external surface of the butterfly proboscis has a sharp boundary separating a hydrophilic drinking region and a hydrophobic non-drinking region. The structural arrangement of the proboscis provides the basis for the wetting dichotomy. Theoretical and experimental analyses show that fluid uptake is associated with enlargement of hydrophilic cuticular structures, the legulae, which link the two halves of the proboscis together. We also show that an elliptical proboscis produces a higher external meniscus than does a cylindrical proboscis of the same circumference. Fluid uptake is additionally facilitated in sap-feeding butterflies that have a proboscis with enlarged chemosensory structures forming a brush near the tip. This structural modification of the proboscis enables sap feeders to exploit films of liquid more efficiently. Structural changes along the proboscis, including increased legular width and presence of a brush-like tip, occur in a wide range of species, suggesting that a wetting dichotomy is widespread in the Lepidoptera.
吸食液体的昆虫的口器具有独特的材料特性，没有人类工程学的类似物：这些取食装置在保持清洁的同时能够获取粘性和粘性液体。我们发现蝴蝶喙的外表面有一个明显的边界，将亲水性的取食区域和疏水性的不取食区域分开。喙的结构排列为润湿二分法提供了基础。理论和实验分析表明，流体的摄取与亲水性表皮结构（legulae）的扩大有关，这些结构将喙的两半连接在一起。我们还表明，椭圆形喙产生的外部弯月面比相同周长的圆柱形喙更高。在吸食树液的蝴蝶中，由于喙上的化学感觉结构增大形成了一个在喙尖附近的刷子，因此流体的摄取更容易。这种喙的结构修饰使吸食树液的蝴蝶能够更有效地利用液体薄膜。在包括增加的 legulae 宽度和存在刷状尖端在内的沿着喙的结构变化在广泛的物种中发生，这表明润湿二分法在鳞翅目昆虫中广泛存在。
