Male description, bionomics, and phylogenetic placement of Phytodietus (Weisia) clavotibialis Shimizu & Konishi (Hymenoptera: Ichneumonidae: Tryphoninae: Phytodietini), with insights into the subgeneric systematics of the genus Phytodietus Gravenhorst.

Phytodietus (Weisia) clavotibialis Shimizu & Konishi, 2018 (Hymenoptera: Ichneumonidae: Tryphoninae: Phytodietini) is a rare and poorly known Darwin wasp, previously known only from the female holotype collected in Japan. In this study, the male is described for the first time based on two specimens. One of these was reared from a tortricid leaf-roller moth feeding on Rhododendron reticulatum D. Don ex G. Don, marking the first host record for both the species and the subgenus Weisia Schmiedeknecht from Tortricidae. New distribution records from India and Taiwan extend the known range of P. (W.) clavotibialis and reveal a biogeographic pattern resembling that of its closest relative, P. (W.) pitambari Kaur & Jonathan, 1979. Partial sequences of mitochondrial CO1 and nuclear 28S rDNA genes were newly obtained, representing the first molecular data for Weisia, and were used in a preliminary phylogenetic analysis. Although the subgenus Euctenopus Ashmead was not included in our analysis, the molecular phylogeny recovered Weisia as the most basal lineage within the genus Phytodietus Gravenhorst, supporting its recognition as a distinct subgenus, while the monophyly of the subgenera Phytodietus and Neuchorus Uchida was not supported. Given the longstanding confusion and our results, it is concluded that these subgenera are best treated as a single subgenus; thus, Neuchorus syn. nov., together with its previously recognized synonym Doratistes Seyrig, is synonymized under Phytodietus. Additionally, P. (W.) clavotibialis appears to be associated with secondary natural environments characteristic of Satoyama landscapes, raising conservation concerns due to ongoing habitat degradation.