Morphology of the pterothoracic musculature in Paraneoptera and its phylogenetic implication (Insecta: Neoptera)

Although the monophyly of Paraneoptera (=hemipteroid orders or Acercaria, composed of Psocodea, Thysanoptera and Hemiptera) has been widely accepted morphologically, the results from molecular phylogenetic and phylogenomic analyses contradict this hypothesis. In particular, phylogenomic analyses provide strong bootstrap support for the sister group relationship between Psocodea and Holometabola, that is, paraphyly of Paraneoptera. Here, we examined the pterothoracic musculature of Paraneoptera, as well as a wide range of other neopterous insect orders, and analysed its phylogenetic implication. By using the synchrotron microcomputed tomography (µCT) and parsimony-based ancestral state reconstruction, several apomorphic conditions suggesting the monophyly of Paraneoptera, such as the absence of the II/IIItpm7, IIscm3, IIIspm2 and IIIscm3 muscles, were identified. In contrast, no characters supporting Psocodea + Holometabola were recovered from the thoracic muscles. These results provide additional support for the monophyly of Paraneoptera, together with the previously detected morphological apomorphies of the head, wing base, and abdomen.