Zeng Yu, Naing Grisanu, Lu Vivian, Chen Yuexiang, Dudley Robert
Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
Department of Integrative Biology, University of South Florida, Tampa, FL 33620, USA.
J Exp Biol. 2024 Dec 15;227(24). doi: 10.1242/jeb.247805. Epub 2024 Dec 16.
Many wingless arboreal arthropods can glide back to tree trunks following free falls. However, little is known about the behaviors and aerodynamics underlying such aerial performance, and how this may be influenced by body size. Here, we studied gliding performance by nymphs of the stick insect Extatosoma tiaratum, focusing on the dynamics of J-shaped trajectories and how gliding capability changes during ontogeny. After being dropped 40 cm horizontally from a visual target, the first-instar nymphs landed on the target within 1.1 s. After reaching terminal speed (at ∼0.25 s), they initiated gliding with significant horizontal force, during which the overall lift-to-drag ratio increased from 0.16 to 0.48. This transition from parachuting to gliding is characterized by a damped oscillation in body pitch, initiated with a rapid nose-down pitching, and led to a higher-lift configuration with reduced body angle of attack. Among instars, increasing wing loading during ontogeny led to greater terminal speed, reduced agility during glide initiation and increased glide angle. Our study demonstrates that a sequence of controlled behaviors, from pre-glide descent to glide initiation and forward gliding, underlies their gliding aerodynamics, which in aggregate form the basis for J-shaped aerial trajectories. Selection for improved gliding performance in wingless arthropods may foster the evolution of more rapid maneuvers and of dedicated morphological traits (such as winglets) that contribute to an overall reduction in wing loading, either across ontogeny or during the evolution of larger body size.
许多无翅树栖节肢动物在自由落体后能够滑翔回到树干。然而，对于这种空中表现背后的行为和空气动力学，以及其如何受到体型影响，我们知之甚少。在这里，我们研究了棘足虫（Extatosoma tiaratum）若虫的滑翔性能，重点关注J形轨迹的动力学以及滑翔能力在个体发育过程中的变化。从视觉目标水平放下40厘米后，一龄若虫在1.1秒内落在目标上。达到终端速度（约0.25秒时）后，它们以显著的水平力开始滑翔，在此期间，整体升阻比从0.16增加到0.48。从降落伞式下降到滑翔的这种转变的特征是身体俯仰的阻尼振荡，始于快速的机头向下俯仰，并导致具有减小的身体迎角的更高升力配置。在各龄若虫中，个体发育过程中增加的翼载荷导致更高的终端速度、滑翔起始时敏捷性降低以及滑翔角增加。我们的研究表明，从滑翔前下降到滑翔起始再到向前滑翔的一系列受控行为是其滑翔空气动力学的基础，这些行为总体上构成了J形空中轨迹的基础。对无翅节肢动物改进滑翔性能的选择可能会促进更快速机动以及有助于整体降低翼载荷的专门形态特征（如小翼）的进化，无论是在个体发育过程中还是在更大体型的进化过程中。
