The digestive system of the adult Hermetia illucens (Diptera: Stratiomyidae) : morphological features and functional properties

The larvae of the black soldier fly (BSF), Hermetia illucens(Linnaeus, 1758) (Diptera: Stratiomyidae), are considered an efficient system for the bioconversion of organic waste into usable products, such as insect protein for animal feed and bioactive molecules. Despite the great interest toward H. illucens and its biotechnological applications, information on the biology of this insect is still scarce. In particular, no data on the structural and functional properties of the digestive system of the adult insect are available and it is a common belief that the fly does not eat. In the present work, we therefore investigate the remodeling process of the BSF larval midgut during metamorphosis, analyze the morphofunctional properties of the adult midgut, evaluate if the fly is able to ingest and digest food and assess whether the feeding supply influences the adult performances. Our results show that the larval midgut of H. illucens is removed during metamorphosis and a new pupal-adult epithelium, characterized by peculiar features compared to the larval organ, is formed by proliferation and differentiation of midgut stem cells. Moreover, our experiments indicate that the adult insect possesses a functional digestive system and that food administration affects the longevity of the fly. These data not only demonstrate that the adult BSF is able to eat but also open up the possibility to manipulate the feeding substrate of the fly to improve its performances in mass rearing procedures.