Nutritional plasticity of the black soldier fly (Hermetia illucens) in response to artificial diets varying in protein and carbohydrate concentrations

Protein (P) and carbohydrate (C) concentrations present in food affect larval performance, larval body nutrient concentration, and fecundity of the black soldier fly (BSF). We substantially expanded the range of dietary P- and C-concentrations investigated thus far to assess the effects of nutritionally - unbalanced diets on BSF larval and adult life-history traits, and on larval body protein and lipid concentrations. Twenty five artificial diets varying in their P- and C-concentration and ratio were formulated. We tested five macronutrient (P+C) concentrations (5, 15, 25, 50 and 75%) and five P:C ratios (1:1, 1:2, 1:4, 2:1 and 4:1). BSF performance was affected by P+C-concentration rather than by P:C ratios. A P-concentration between 10 and 15% and a C-concentration between 10 and 60% supported high larval and adult performance. P-concentration is limiting for most of the performance variables, however, a P-concentration higher than 37% reduced larval survival. C-concentration affected egg production more strongly than P-concentration. Overall, at P+C values of 25 and 50%, and P:C ratios 1:2 and 1:4 resulted in the highest values of most of the larval and adult performance variables we measured. For the protein and carbohydrate sources tested, dietary macronutrient concentrations significantly affected larval and adult performance of BSF in different ways. These results show a remarkable degree of nutritional plasticity, and point to the relevance of differentiating the formulation of diets to achieve maximal larval yield, high body protein or high body lipid accumulation or high adult emergence and egg production.