Western Palearctic Leptopilina wasps revised with updated world species list

A taxonomic revision of the parasitoid wasp genus Leptopilina has identified seven species in the Western Palearctic and produced an updated identification key based on morphology and mitochondrial CO1 barcodes. The study also compiled the known global species, biological records, distributions and host relationships of the genus, providing a consolidated reference for specialists studying these wasps.

The researchers combined morphological examination of 91 Western Palearctic specimens with CO1 sequence data and additional museum material. The sequenced specimens represented five morphologically distinct species: Leptopilina clavipes, L. fimbriata, L. heterotoma, L. japonica and L. longipes. Three species-delimitation methods applied to the sequence data recognized the same five clusters, and those clusters corresponded to the authors’ morphological identifications. No specimen of the rarely collected L. australis was successfully sequenced, while L. boulardi was not included in the molecular analysis because the authors did not morphologically examine the corresponding specimens.

The resulting identification key uses features of the metapleuron, mesoscutellum, antennae, forewing venation, propodeal carinae and coloration. The authors deliberately avoided relying on rows of setae on the mesoscutum to separate L. clavipes from L. australis, because these setae can be lost during collection and handling. Mesoscutellar characters were retained but treated cautiously because their form varies and can overlap among species. The key applies to both sexes.

The revision documented a previously unrecognized diagnostic character for L. japonica: unlike most other Western Palearctic species, it has no distinct patch of setae at the base of the metacoxa, although a few isolated setae may be present. This feature, consistent in the authors’ material, helps distinguish the species from L. heterotoma, which is morphologically similar and is also frequently studied in laboratory and field research.

The study also summarized literature, museum-label information and major collecting projects to describe the habitats, adult flight periods, host records and population parameters of the seven regional species. The synthesis indicates ecological differences among them. L. boulardi, L. heterotoma and L. japonica are primarily associated with fruit, although L. heterotoma also uses plant detritus and fungi. L. australis and L. fimbriata are primarily associated with plant detritus, while L. clavipes and L. longipes are chiefly associated with fungi but also occur in decaying plant material.

Host records were separated into observations made in the field and records obtained through laboratory rearing, with additional distinctions for the quality of the host evidence. L. heterotoma was described as a generalist with a broad range of drosophilid hosts, whereas L. fimbriata had been found only from Scaptomyza pallida and Drosophila subobscura. L. boulardi attacks Drosophila suzukii but cannot develop in that host, whereas L. japonica can overcome its immune response. The authors noted that L. heterotoma eggs in D. suzukii are encapsulated and the wasp does not develop successfully.

The compiled distribution records document the continued presence and spread of the non-native L. japonica in Europe. The species has been recorded from Belgium, France, Germany, Italy, Switzerland and the United Kingdom, as well as Canada and the United States. The study included two previously unpublished 2022 records, from Bonn in Germany and Ypres in Belgium; the Ypres specimen represented a new country record. These observations are records of occurrence and do not by themselves establish changes in population size or the ecological effects of the species on native Leptopilina.

Beyond the Western Palearctic, the authors compiled species lists for the Eastern Palearctic, Oriental, Nearctic, Afrotropical, Oceanian/Australasian and Neotropical regions. They also made several taxonomic changes, including moving Leptopilina novicia to the genus Hexacola, placing Ditanyomeria and Hexarhoptra in synonymy with Leptopilina, and transferring additional names into the genus. The authors emphasized that knowledge remains uneven, with relatively few records from Eastern Europe, little information on L. australis, and potentially synonymous or undescribed species in several regions.

The revision is constrained by incomplete and unevenly distributed occurrence data, the absence of a CO1 sequence for L. australis, and the exclusion of L. boulardi from the new molecular analyses. Several barcode clusters in public databases also contain misidentified specimens and require taxonomic review. The study therefore provides a revised regional framework rather than a complete account of global diversity, with its identification key, biological synthesis and regional species lists intended to support subsequent taxonomic and field research.

Subject of Research: Taxonomic revision and identification of Western Palearctic Leptopilina parasitoid wasps

Article Title: The Leptopilina Förster, 1869 of the Western Palearctic, and an updated list of the world species ( Hymenoptera , Figitidae , Eucoilinae )

Article References: Vogel, J., Martin, J., Forshage, M., Salden, T., Staverløkk, A., Verheyde, F., Nordlander, G., Herz, A., & Peters, R. S. (2025). The Leptopilina Förster, 1869 of the Western Palearctic, and an updated list of the world species (Hymenoptera, Figitidae, Eucoilinae). Journal of Hymenoptera Research, 98, 915-969. https://doi.org/10.3897/jhr.98.165583

Image Credits: AI Generated

DOI: 10.3897/jhr.98.165583

Keywords: Leptopilina, Figitidae, Eucoilinae, taxonomic revision, integrative taxonomy, CO1 barcoding, parasitoid wasps, Western Palearctic, species identification, Drosophilidae, rster, Western