Characterization of preimaginal developmental stages of two cryptic South African species of the Merodon planifacies complex (Diptera: Syrphidae: Eristalinae: Merodontini), with differentiation through morphometry analysis

Merodon capi Vujić et Radenković, 2020 and Merodon roni Radenković et Vujić, 2020 are two cryptic species belonging to the Merodon planifacies Bezzi, 1915 species complex that have recently been described, with the differences between them being revealed by molecular and geometric morphometry studies of adult specimens. In the present study, the preimaginal morphology of both species is described and displayed, with the material used corresponding to samples taken from bulbs of Merwilla plumbea (Lindl.) Speta plants at two locations in KwaZulu-Natal province (South Africa). The preimaginal stages were compared, looking for morphological evidence supporting species divergence. Linear and geometric morphometric analyses of the larval posterior respiratory process were conducted for the first time and the results of these analyses support the separation of the two taxa. Information about the life cycle and the relation with the host plant is also provided. In addition, we carried out a preliminary study of the adult feeding requirements of the species, based on the description of the mouthparts and an analysis of the pollen present in the gut and on the integument of adults. The results of the study supports a close relationship between the preimaginal stages and plant species of the Hyacinthaceae family.

The study was mainly funded by the European Union project: Horizon 2020, Marie Skłodowska-Curie Actions, Research and Innovation Staff Exchange (RISE) Programme: FlyHigh – “Insect–plant relationships: insights into biodiversity and new applications” (project 645636). The study was partly supported by the Ministry of Education, Science and Technological Development, Republic of Serbia, Grant No. 451-03-68/2022–14/200125 and Grant No. 451-03-68/2022–14/200358. It was also supported by the research department of the University of Alicante in the framework of a predoctoral grant (UAFPU2019-03). This manuscript was written as a part of a PhD project conducted by Andrea Aracil at the University of Alicante (Spain).