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The tracheal (respiratory) system is regarded as one of the key elements which enabled insects to conquer terrestrial habitats and, as a result, achieve extreme species diversity. Despite this fact, anatomical data concerning this biological system is relatively scarce, especially in an ontogenetic context. The purpose of this study is to provide novel and reliable information on the post-embryonic development of the tracheal system of holometabolous insects using micro-computed tomography methods. Data concerning the structure of the respiratory system acquired from different developmental stages (larvae, pupae and adults) of a single insect species (Tenebrio molitor) are co-analysed in detail. Anatomy of the tracheal system is presented. Sample sizes used (29 individuals) enabled statistical analysis of the results obtained. The following aspects have been investigated (among others): the spiracle arrangement, the number of tracheal ramifications originating from particular spiracles, the diameter of longitudinal trunks, tracheal system volumes, tracheae diameter distribution and fractal dimension analysis. Based on the data acquired, the modularity of the tracheal system is postulated. Using anatomical and functional factors, the following respiratory module types have been distinguished: cephalo-prothoracic, metathoracic and abdominal. These modules can be unambiguously identified in all of the studied developmental stages. A cephalo-prothoracic module aerates organs located in the head capsule, prothorax and additionally prolegs. It is characterised by relatively thick longitudinal trunks and originates in the first thoracic spiracle pair. Thoracic modules support the flight muscles, wings, elytra, meso- and metalegs. The unique feature of this module is the presence of additional longitudinal connections between the neighbouring spiracles. These modules are concentrated around the second prothoracic and the first abdominal spiracle pairs. An abdominal module is characterised by relatively thin ventral longitudinal trunks. Its main role is to support systems located in the abdomen; however, its long visceral tracheae aerate organs situated medially from the flight muscles. Analysis of changes of the tracheal system volume enabled the calculation of growth scaling among body tissues and the volume of the tracheal system. The data presented show that the development of the body volume and tracheal system is not linear in holometabola due to the occurrence of the pupal stage causing a decrease in body volume in the imago and at the same time influencing high growth rates of the tracheal system during metamorphosis, exceeding that ones observed for hemimetabola.

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Morphological, anatomical, and distributional data concerning the South African endemic beetle subtribe Pythiopina (Tenebrionidae: Pedinini) are revised. Five species, representing two genera, are recognized. Included in this total is one new species (Meglyphus mariae Kamiński sp.n.). The following species are placed in synonymy: Meglyphus ciliatipes [=Meglyphus calitzensis syn.n.]; Meglyphus laenoides [=Meglyphus andreaei syn.n.; =Meglyphus namaqua syn.n.].Microtomographic models for all valid Pythiopina species, including the holotype of the newly described species, are presented and analysed. Endoskeleton morphology (specifically characters of the tentorium and metendosternite) proved to be informative at the specific and generic levels. An identification key is provided to all known species of the subtribe. Environmental niche models are presented for the majority of species. A molecular phylogeny of Pedinini based on six genetic loci (28S: D1-D3 region; 28S: D4-D5 region, COII, ArgK, CAD2, wg) was also produced to explore the phylogenetic position of Pythiopina. This analysis is the first to include representatives of all seven subtribes of Pedinini, and supports a sister relationship between Pythiopina and the Palaearctic subtribe Dendarina. Results also suggest the existence of a second pair of sister taxa within Pedinini (in addition to Melambiina) with an amphitropical African distribution.This published work has been registered in ZooBank, http://zoobank.org/urn:lsid: zoobank.org:pub

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