Beyond Hermetia illucens: An investigation of the garden soldier fly Exaireta spinigera as a potential bioconverter of food waste

Using insects to convert food waste into useable products, such as livestock feed, is an elegant solution to the twin crises of waste disposal and food production. To date, the black soldier fly (Hermetia illucens) has garnered intense research interest as an excellent bioconverter that consumes wastes and converts them into high protein larval biomass that can be fed to livestock or used to make biodiesel. However, other members of the soldier fly family (Stratiomyidae) have received far less attention despite similar life‐history traits. Here, we examine the seasonality and performance (protein content and protein conversion efficiency) of larval Australian garden soldier flies, Exaireta spinigera. We first examined the state of knowledge about E. spinigera's biology and life history via a literature search. Next, we used a global biodiversity database to infer the seasonality of E. spinigera in Australia. Finally, we conducted outdoor feeding experiments to investigate protein content and protein conversion efficiency of larvae fed wastes ranging from 100% fruit and vegetable waste (low protein) to 100% poultry feed (higher protein). E. spinigera appears to be a autumn/spring active species, with reported sightings peaking during cooler months of the year. E. spinigera larvae also dominated outdoor bucket traps during the winter, when H. illucens was otherwise inactive. E. spinigera larvae had decreased protein content and decreased protein conversion efficiency when fed foods that contained a high proportion of low‐protein food waste. However, even in the 100% food waste treatment, the protein content of E. spinigera was relatively high at 38.6% crude protein. We suggest that E. spinigera is an excellent candidate for further research as it can convert low‐quality food waste into high protein larvae at colder temperatures than H. illucens. Our results highlight the benefits of investigating a wider range of dipteran species for their bioconversion abilities.