Metamorphosis remains one of the most complicated and poorly understood processes in insects. This is particularly so for the very dynamic transformations that take place within the pupal sheath of holometabolous insects. Only few studies address these transformations especially with regard to cranial structures of those holometabolous species where the larval and adult forms have a similar diet. It thus remains unclear to what extent the internal structures undergo histolysis and rebuilding. Here, the development of the brain and skeleto-muscular system of the head of Chrysopa pallens (Rambur, 1838) is studied. This species is a predator of aphids in the larval and adult stage. We used micro-computed-tomography (μ-CT) to study the transformations of the larval, prepupal and pupal head within the cocoon. We first assessed the morphological differences and similarities between the stages. We then determined the point in time when the compound eyes appear and describe the re-orientation of the head capsule which transforms the prognathous larva into a hypognathous adult. The internal head muscles are distinctly more slender in larvae than adults. In addition, the adults have a significantly larger brain which is likely needed for the processing of the signals obtained by the adults vastly expanded sensory organs that are presumably needed for dispersal and mating. Our study shows that the histolysis and modification of the inner muscles and skeletal elements take place within the prepupa. The central nervous system persists throughout metamorphosis but its morphology changes significantly. Our study reveals that not only the inner structures, but also the outer morphology continues to change after the final larval moult. The adult cuticle and internal structures form gradually within the cocoon. The histolysis and rebuilding begin with the skeletal elements and is followed by changes in the central nervous system before it concludes with modifications of the musculature. This order of events is likely ancestral for Holometabola because it is also known from Hymenoptera, Diptera, Mecoptera, and Coleoptera.

中文翻译：

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有助于理解同化进化：在绿色草wingChrysopa pallens（Neuroptera：Chrysopidae）的变态过程中，内部头部结构的转变。

变态仍然是昆虫中最复杂，最难理解的过程之一。对于在全代谢昆虫的sheath鞘内发生的非常动态的转化尤其如此。只有很少的研究解决了这些转变，特别是关于那些在幼虫和成虫的饮食相似的全代谢物种的颅骨结构方面。因此，尚不清楚内部结构在多大程度上经历了组织溶解和重建。在这里，研究了Chrysopa pallens（Rambur，1838）头部的大脑和骨骼肌肉系统的发育。该物种是幼虫和成年期的蚜虫捕食者。我们使用微计算机断层扫描（μ-CT）研究了茧内幼虫，pu前和p的转化。我们首先评估了两个阶段之间的形态差异和相似性。然后，我们确定了复眼出现的时间点，并描述了头囊的重新定向，该头囊将脱垂幼虫转变为下垂成虫。与成人相比，幼虫的内部头部肌肉明显更细长。另外，成年人的大脑明显更大，这可能是处理成年人广泛扩张的感觉器官所需的信号所需要的，而这些器官可能是散布和交配所必需的。我们的研究表明，内部肌肉和骨骼元素的组织分解和修饰发生在prepupa内。中枢神经系统在整个变态过程中持续存在，但其形态发生了显着变化。我们的研究表明，不仅内部结构，但最终的幼体换羽后，外部形态仍在继续变化。成年的表皮和内部结构在茧内逐渐形成。组织溶解和重建始于骨骼元素，然后是中枢神经系统的变化，然后才结束肌肉组织的改变。这种事件的顺序可能是Holometabola的祖先，因为它在膜翅目，双翅目，中翅目和鞘翅目中也是众所周知的。