Department of Biology, Lund University, 22362 Lund, Sweden.
J R Soc Interface. 2012 Oct 7;9(75):2745-8. doi: 10.1098/rsif.2012.0053. Epub 2012 May 16.
Flying insects typically possess two pairs of wings. In beetles, the front pair has evolved into short, hardened structures, the elytra, which protect the second pair of wings and the abdomen. This allows beetles to exploit habitats that would otherwise cause damage to the wings and body. Many beetles fly with the elytra extended, suggesting that they influence aerodynamic performance, but little is known about their role in flight. Using quantitative measurements of the beetle's wake, we show that the presence of the elytra increases vertical force production by approximately 40 per cent, indicating that they contribute to weight support. The wing-elytra combination creates a complex wake compared with previously studied animal wakes. At mid-downstroke, multiple vortices are visible behind each wing. These include a wingtip and an elytron vortex with the same sense of rotation, a body vortex and an additional vortex of the opposite sense of rotation. This latter vortex reflects a negative interaction between the wing and the elytron, resulting in a single wing span efficiency of approximately 0.77 at mid downstroke. This is lower than that found in birds and bats, suggesting that the extra weight support of the elytra comes at the price of reduced efficiency.
飞行昆虫通常拥有两对翅膀。在甲虫中，前一对翅膀已经进化成短而坚硬的结构，即鞘翅，它保护第二对翅膀和腹部。这使得甲虫能够在其他情况下会损坏翅膀和身体的环境中生存。许多甲虫在伸展鞘翅的情况下飞行，这表明它们影响空气动力学性能，但关于它们在飞行中的作用知之甚少。我们通过对甲虫尾迹的定量测量表明，鞘翅的存在使垂直力的产生增加了约 40%，表明它们有助于支撑重量。与之前研究的动物尾迹相比，翅膀和鞘翅的组合产生了复杂的尾迹。在中下降阶段，每个翅膀后面都可以看到多个涡流。这些涡流包括翼尖涡流和具有相同旋转方向的鞘翅涡流、体涡流和相反旋转方向的附加涡流。后一个涡流反映了翼和鞘翅之间的负相互作用，导致中下降阶段的单个翼展效率约为 0.77。这低于鸟类和蝙蝠的发现，表明鞘翅的额外重量支撑是以降低效率为代价的。
