Flies are what they eat : Tailoring nutrition of Black Soldier Fly (Hermetia illucens L.) for larval biomass production and fitness

Black Soldier Fly – BSF; Hermetia illucens L. (Diptera: Stratiomyidae) has been proposed as one of the most suitable insect species to be used as animal feed. Advantages of using BSF that have been identified are their capacity to convert organic waste, to reduce the numbers of certain harmful bacteria and insect pests, to provide potential chemical precursors to produce biodiesel, and to provide high quality protein to be used as feed for a variety of animals. This thesis explores nutritional physiology of BSF and its effect on larval biomass production and fitness. Knowing the physiological mechanisms that BSF employs to deal with different nutrient concentrations, and their impacts on BSF life-history traits and larval body content, may yield valuable insights into the nutritional ecology of BSF. Experiments involving the study of larval densities, total nutrient content, and dietary protein (P) and carbohydrate (C) content and ratio on artificial, semi-artificial and organic residual stream diets were used to unravel their effect on life-history traits, body nutrient content and reproduction of BSF. Results presented in this thesis show that larval density and nutrient content interact at low nutrient content to affect BSF larval performance and body composition, nutrient content overall having a stronger effect. Regarding dietary protein and carbohydrate, I conclude that BSF has post-ingestive mechanisms to deal with imbalanced foods. Carbohydrate-biased P:C ratios positively affect BSF performance, both on the artificial diets and the organic residue stream, P-content being limiting for most of the performance variables. In the experiments throughout this study larval protein content was high and largely independent of dietary protein content, although small differences were found between treatments. However, larval crude fat varied over a wider range depending on dietary macronutrient content, protein content affecting larval crude fat content to a large extent. The data presented in this thesis contribute to our understanding of how nutrition, mainly in terms of protein and carbohydrate content and ratio, affects life-history traits, nutrient body content and reproduction of BSF and how this knowledge can be applied to improve the productive performance and larval body composition in BSF production systems.