The adult Hermetia illucens (Diptera: Stratiomyidae) is endowed with a functional digestive system

The larvae of black soldier fly (BSF), Hermetia illucens, emerge as a relevant resource of protein since they can convert low-quality biomass into nutritionally valuable proteins. Despite the great interest on the use of these larvae by the emerging industrial sector of edible insects, information on the biology of this insect is still scarce. In particular, no information on the structural and functional properties of the digestive system of the adult BSF is available and only few data about the feeding habits of the fly are present in the literature. In the present work, we investigated the remodeling process that occurs in H. illucens larval midgut during metamorphosis. In addition, we analyzed the morphology and function of the adult midgut, and evaluated the feeding habits of the fly. Our results demonstrate that the larval midgut epithelium of H. illucens is removed during metamorphosis and a new pupal-adult epithelium is formed by proliferation and differentiation of intestinal stem cells. During this process, a mobilization of long-term storage molecules, i.e., glycogen and lipids, occurs. Moreover, in contrast to what many literature records have reported so far, our data indicate that the adult insect has a functional digestive system, and that food administration affects the longevity of the fly. This new scenario not only opens up the possibility to manipulate the feeding substrate of the fly to improve its performances in mass rearing procedures, but could also provide insights into the safety of using this insect for feed production.