Novel trophic interaction: the scuttle fly Megaselia scalaris (Diptera: Phoridae) is a facultative parasitoid of the desert scorpion Mesobuthus eupeus mongolicus (Scorpiones: Buthidae)

Clear knowledge about trophic interactions among species contributes to understanding biodiversity structuring and ecosystem functioning. However, identification of host-parasitoid interactions is often impeded by the hyper-diversity of parasitoid community and their immature stages under study. As a consequence, our knowledge on host-parasitoid interactions is rather incomplete and many trophic links are still missing. In this study, we discovered that the scuttle fly Megaselia scalaris (Loew 1866) facultatively infested the scorpions of Mesobuthus eupeus mongolicus (Birula, 1911). We monitored the parasitoidism process in laboratory and obtained the parasitoid adults. The parasitoids were identified by examination of morphological characteristics and genetic analyses of mitochondrial DNA sequences from both larvae and adults. Ecological niche modelling revealed that climatically suitable areas for both parasitoids and scorpions stretch in northwest China. Our results unveiled the missing trophic links between Phoridae and Buthidae, and our morphological description and genetic inventory will provide the basic data for future studies on the exceptionally polyphagous and cosmopolitan insect species, M. scalaris.