Abstract：
To probe its environment, the flying insect controllably flexes, twists, and maneuvers its antennae by coupling mechanical deformations with the sensory output. We question how the materials properties of insect antennae could influence their performance. A comparative study was conducted on four hawkmoth species: Manduca sexta, Ceratomia catalpae, Manduca quinquemaculata, and Xylophanes tersa. The morphology of the antennae of three hawkmoths that hover while feeding and one putatively non-nectar-feeding hawkmoth (Ceratomia catalpa) do not fundamentally differ, and all the antennae are comb-like (i.e., pectinate), markedly in males but weakly in females. Applying different weights to the free end of extracted cantilevered antennae, we discovered anisotropy in flexural rigidity when the antenna is forced to bend dorsally versus ventrally. The flexural rigidity of male antennae was less than that of females. Compared with the hawkmoths that hover while feeding, Ceratomia catalpae has almost two orders of magnitude lower flexural rigidity. Tensile tests showed that the stiffness of male and female antennae is almost the same. Therefore, the differences in flexural rigidity are explained by the distinct shapes of the antennal pectination. Like bristles in a comb, the pectinations provide extra rigidity to the antenna. We discuss the biological implications of these discoveries in relation to the flight habits of hawkmoths. Flexural anisotropy of antennae is expected in other groups of insects, but the targeted outcome may differ. Our work offers promising new applications of shaped fibers as mechanical sensors. STATEMENT OF SIGNIFICANCE: Insect antennae are blood-filled, segmented fibers with muscles in the two basal segments. The long terminal segment is muscle-free but can be flexed. Our comparative analysis of mechanical properties of hawkmoth antennae revealed a new feature: antenna resistance to bending depends on the bending direction. Our discovery replaces the conventional textbook scenario considering hawkmoth antennae as rigid rods. We showed that the pectinate antennae of hawkmoths behave as a comb in which the bristles resist bending when they come together. This anisotropy of flexural resistance offers a new mode of environmental sensing that has never been explored. The principles we found apply to other insects with non-axisymmetric antennae. Our work offers new applications for shaped fibers that could be designed to sense the flows.
摘要：
为了探测它的环境，飞行昆虫可控地弯曲，曲折，并通过将机械变形与感官输出耦合来操纵其触角。我们质疑昆虫触角的材料特性如何影响其性能。对四种鹰蛾物种进行了比较研究：Manducasexta，CatalpaeCeratomia,曼杜卡五号库拉塔，和Xylophanestersa。在取食时盘旋的三个鹰蛾的触角形态和一个假定为非花蜜的鹰蛾（Ceratomiacatalpa）没有根本区别，并且所有的天线都是梳状的(即，果胶)，在男性中明显，但在女性中较弱。对提取的悬臂天线的自由端施加不同的重量，当天线被迫向背侧和腹侧弯曲时，我们发现了弯曲刚度的各向异性。男性触角的弯曲刚度小于女性。与喂食时盘旋的鹰蛾相比，Catalpae的弯曲刚度降低了几乎两个数量级。拉伸测试表明，雄性和雌性触角的刚度几乎相同。因此,弯曲刚度的差异可以通过触角果胶的不同形状来解释。像梳子里的刷毛，这种弯曲为天线提供了额外的刚度。我们讨论了这些发现与鹰蛾的飞行习惯有关的生物学意义。在其他昆虫群体中，天线的弯曲各向异性是预期的，但目标结果可能有所不同。我们的工作为成形纤维作为机械传感器提供了有希望的新应用。重要声明：昆虫触角充满血液，在两个基底段有肌肉的分段纤维。长末端节段无肌肉，但可以弯曲。我们对鹰蛾天线的机械性能的比较分析揭示了一个新特征：天线对弯曲的抵抗力取决于弯曲方向。我们的发现取代了传统的教科书场景，将鹰蛾触角视为刚性杆。我们表明，鹰蛾的梳状触角表现为梳子，刷毛在一起时会抵抗弯曲。弯曲阻力的这种各向异性提供了一种从未探索过的新的环境传感模式。我们发现的原理适用于其他具有非轴对称触角的昆虫。我们的工作为可以设计用于感测流动的成形纤维提供了新的应用。
