Rethinking houseflies: from pest to production animal in the circular economy

Abstract As current agricultural production poses an increasing environmental burden, there is an urgent need to develop more sustainable practices to feed a growing world population. The use of insects in food and feed production can enhance the resource use efficiency of our food system, as they can grow on various wastes and underutilised by-products from food and biofuel production. Houseflies are receiving increasing interest due to their potential to utilize low-value residual organic streams, such as manure. An important aspect of housefly production systems is the larval interaction with their rearing substrate, which serves both as feeding and living environment. This comprehensive review focusses on the nutritional ecology of housefly larvae in the context of their industrial application. First, a brief description of the housefly’s lifecycle and reproduction relevant to mass rearing is given. Subsequently, relevant substrate conditions, nutrient requirements, the morphology of the feeding apparatus, and their digestive physiology are described. This is followed by a description of larval diets, their waste management and bioconversion potential, and the resulting larval composition, including potential contaminants. Finally, the suitability of housefly larvae as feed ingredient and other applications such as biofuel or other derived products is briefly discussed. Throughout conclusions are provided and gaps of knowledge and promising fields of research are identified. Whereas a strong foundation of knowledge is available for the application of housefly larvae as bio-converters, a concerted effort of academics, producers and legislators is needed to realize the full potential of the housefly in the circular economy.