Insect wings are generally constructed from veins and solid membranes. However, in the case of the smallest flying insects, the wing membrane is often replaced by hair-like bristles. In contrast to large insects, it is possible for both bristled and membranous wings to be simultaneously present in small insect species. There is therefore a continuing debate about the advantages and disadvantages of bristled wings for flight. In this study, we experimentally tested bristled robotic wing models on their ability to generate vertical forces and scored aerodynamic efficiency at Reynolds numbers that are typical for flight in miniature insects. The tested wings ranged from a solid membrane to a few bristles. A generic lift-based wing kinematic pattern moved the wings around their root. The results show that the lift coefficients, power coefficients and Froude efficiency decreased with increasing bristle spacing. Skin friction significantly attenuates lift production, which may even result in negative coefficients at elevated bristle spacing and low Reynolds numbers. The experimental data confirm previous findings from numerical simulations. These had suggested that for small insects, flying with bristled instead of membranous wings involved less change in energetic costs than for large insects. In sum, our findings highlight the aerodynamic changes associated with bristled wing designs and are thus significant for assessing the biological fitness and dispersal of flying insects.
Insects comprise the smallest actively flying animals. Within this highly diverse group, some insects have undergone extreme miniaturization to body sizes smaller than a few hundred micrometres (Polilov, 2015). Such extreme reduction of a complex multicellular organism to the size of a large unicellular organism is bound to require adjustments of sensory organs (Fischer et al., 2011; Sane, 2016), the nervous (Polilov, 2012) and reproduction (Minelli & Fusco, 2018) systems, thorax musculature (Yavorskaya et al., 2019), wing shape (Rensch, 1948) and overall physiology. Such extreme adjustments make the needs and functioning of these insects distinct from that of larger ones.Miniature insects tend to have a narrower wing plate surrounded by long bristles (Rensch, 1948) and reduced number of wing-veins (Polilov, 2015). These wing features are regarded as an
Malignant peripheral nerve sheath tumors are rare and most often appear in the clinical setting of yon Recklinghausen's neruofibromatosis. On rare occasions they are seen in patients lacking any of the overt stigmata of this systemic disease. We report on a case of a peripheral nerve sheath sarcoma (PNSS) on the scalp and the back of the neck of a 13-year-old female arising in a solitary benign neurofibroma with no evidence of systemic neurofibromatosis. The tumor was examined by ultrastructural and immunohistochemical techniques as well as by routine histopathology. It was defined as a peripheral nerve sheath sarcoma, fibrosarcomatous type, of poorly differentiated perineurial cell origin. The possible significance of histogenetic subclassification in terms of surgical management and the oncological approach as well as the prognosis is discussed.
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