![]() Recent studies have shown that the aerodynamic performance of MAVs, such as ‘Delfly’, which has been equipped with rather slack, sail-like wings, may be improved through structural rigidity imparting veins, which enable directed passive deformations, minimise wing tear and increase the fracture toughness and, thus, the stability of a wing (Wootton, 1981, 1991 Newman, 1982 Wootton & Newman, 2008 Lentink et al. The latter are small autonomous or remotely controlled aircrafts, designed for the reconnaissance in confined and poorly accessible space. Additionally, some recent studies aimed to draw inspiration from their wing design, in order to improve the performance of so-called micro-air vehicles (MAVs). These characteristics of odonate wings are beneficial for the investigation of wing structure and material composition, particularly with respect to flight. As members of the extant Paleoptera, Odonata do not have the ability to fold their wings (Kukalová-Peck, 1974 Willkommen, 2009), as do the representatives of Neoptera, which are more adapted to terrestrial locomotion. As in all winged insects, their wings lack internal muscles and, thus, deform passively during flight, driven by aerodynamic but mainly by inertial forces (Wootton, 1981, 1991 Newman, 1982 Wootton & Newman, 2008 Jongerius & Lentink, 2010). Their flight performance has been the subject of various aerodynamic, kinematic and morphological studies (Wootton, 1981, 1991 Newman, 1982 Rüppell, 1989 Vargas et al. These results may be relevant not only for biologists, but may also contribute to optimise the design of micro-air vehicles.ĭragonflies and damselflies propel themselves through the air at speeds of partly more than 10 m s −1, and show an exceptional high lift production and manoeuvrability (Nachtigall, 1977 Azuma & Watanabe, 1988 Rüppell, 1989 Okamoto et al. This is especially important in the highly stressed longitudinal veins, which have much lower possibility to yield to applied loads with the aid of vein joints, as the cross veins do. The presence of resilin in the unsclerotised endocuticle suggests its contribution to an increased energy storage and material flexibility, thus to the prevention of vein damage. Longitudinal and cross veins differ significantly in relative thickness of exo- and endocuticle, with cross veins showing a much thicker exocuticle. In wing veins of MBB, the latter are densely packed with light-scattering spheres, previously shown to produce structural colours in the form of quasiordered arrays. Wing veins were shown to consist of up to six different cuticle layers and a single row of underlying epidermal cells. In order to elucidate the wing vein ultrastructure and the exact localisation of resilin in the internal layers of the vein cuticle, the approaches of bright-field light microscopy, wide-field fluorescence microscopy, confocal laser-scanning microscopy, scanning electron microscopy and transmission electron microscopy were combined. Combined with other structural features of wing veins, such as number and thickness of cuticle layers, material composition, and cross-sectional shape, resilin most probably has an effect on the vein′s material properties and the degree of elastic deformations. The present study revealed that resilin is not only present in wing vein joints, but also in the internal cuticle layers of veins in wings of Sympetrum vulgatum (SV) and Matrona basilaris basilaris (MBB). It has already been found in wing vein joints, connecting longitudinal veins to cross veins, and was shown to endow the dragonfly wing with chordwise flexibility, thereby most likely influencing the dragonfly’s flight performance. Resilin, a rubber-like protein, has been suggested to be a key component in insect wing flexibility and deformation in response to aerodynamic loads, and has been reported in various arthropod locomotor systems. Morphological and kinematic investigations have showed that dragonfly wings, though being rather stiff, are able to undergo passive deformation during flight, thereby improving the aerodynamic performance. ![]() Their exceptional aerodynamic performance has been the subject of various studies. Dragonflies count among the most skilful of the flying insects.
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