A taxonomic revision of the genus Alexeter Förster (Hymenoptera, Ichneumonidae, Ctenopelmatinae, Mesoleiini) from Taiwan, with descriptions of six new species

The genus Alexeter Förster, 1869 is first recorded from Taiwan. One previously described species, A. shakojiensis Uchida, 1930, is newly recorded from Taiwan. Six new species, A. flavomaculatus sp. nov., A. hsiaoae sp. nov., A. mediolobus sp. nov., A. monticola sp. nov., A. pseudozangicus sp. nov., and A. rufispeculus sp. nov., are described and can be distinguished from their congeners primarily based on color pattern, mandibular teeth, propodeal carinae, fore wing length and venation, ocellar and first metasomal tergite measurements, and flagellomere counts.

Illustrations of the male genitalia and a diagnostic key to the Taiwanese Alexeter species are provided. DNA-based species delimitations are provided as supporting evidence for four new species. In a COI-based phylogeny sampling 31 operative taxonomic units of Alexeter and similar genera, the genus Alexeter was not resolved as a monophyletic group.

Additionally, the COI barcode showed limitations in distinguishing some Alexeter morphospecies, indicating the need for further evaluation of COI - based species delimitation in this genus.