First record of Aximopsis s.l. (Hymenoptera, Eurytomidae) from China, with description of a new species parasitising the larvae of the coastal pollinator Ceratina smaragdula (Hymenoptera, Apidae).

BACKGROUND: The genus Aximopsis sensu lato (Hymenoptera, Eurytomidae) is a cosmopolitan group of parasitoid wasps, currently comprising 43 described species. The genus is defined by a suite of homoplastic morphological characters and its taxonomic boundaries remain unstable, with recent molecular phylogenies indicating paraphyly. The nodularis species group, which accounts for approximately half of the known species, includes parasitoids of various endophytic insects. While host associations with small carpenter bees of the genus Ceratina (Apidae) have been documented for a few eurytomid species in Europe and North America, no species of Aximopsis s.l. has ever been recorded from China.

NEW INFORMATION: A new species of Aximopsis Ashmead, Aximopsis qiong Li, Zhang & Chen sp. nov. (Hymenoptera, Chalcidoidea, Eurytomidae) is described from Hainan, China. The species was reared as a gregarious ectoparasitoid of the small carpenter bee Ceratina smaragdula (Fabricius) (Hymenoptera, Apidae). The new species is provisionally placed in Aximopsis sensu lato and tentatively assigned to the nodularis species group based on morphological characters. Diagnostic characters, detailed morphology, biological observations and illustrations of both sexes are provided. Molecular phylogenetic analysis, based on COI sequences,failed to recover Aximopsis sensu lato as monophyletic, supporting previous evidence of its uncertain generic boundaries. This discovery represents the first record of the genus Aximopsis from China and only the second confirmed species of the nodularis group associated with Ceratina hosts. Collectively, our finding expand the known distribution and host range of this parasitoid lineage, while also underscoring the pressing need for a comprehensive taxonomic revision of Aximopsis sensu lato .