The black soldier fly (BSF; Hermetia illucens L.; Diptera: Stratiomyidae) has been studied for its capability to convert organic waste to high quality protein, control certain harmful bacteria and insect pests, provide potential chemical precursors to produce biodiesel and for its use as feed for a variety of animals. Nutritional value of BSF larvae is discussed, as well as the effect of biotic and abiotic factors on both larval body composition and performance. Although BSF larvae contain high protein levels (from 37 to 63% dry matter; DM), and other macro- and micronutrients important for animal feed, the available studies on including BSF larvae in feed rations for poultry, pigs and fish suggest that it could only partially replace traditional feedstuff, because high or complete replacement resulted in reduced performance. This is due to factors such as high fat content (from 7 to 39% DM), ash (from 9 to 28% DM), and consequences of processing. Therefore, further studies are needed on nutrient composition, digestibility and availability for target species and on improved methods to process larvae, among other aspects. Additionally, it is clear that factors including quantity and quality of food, temperature, substrate moisture and/or larval crowding can affect BSF performance. However, the biology of BSF, in particular of the adult stage, has not been studied in detail. This review provides background information on the nutritional value of BSF larvae, its suitability as animal feed, biotic and abiotic conditions that affect its performance, and identifies which knowledge is required to ensure more dependable yields of BSF-mass rearing and development of economically feasible methods to take advantage of this species as animal feed.

Performance and body composition of insect larvae depend on quality and quantity of their diet, and on biotic factors such as larval density. We investigated the effect of dietary nutrient concentration and larval rearing density on survival, development, growth, and protein and fat contents of larvae of the black soldier fly (BSF), Hermetia illucens L. (Diptera: Stratiomyidae). Neonate larvae were fed with a low (NC1), intermediate (NC2), or high nutrient concentration (NC3), and with four rearing densities (50, 100, 200, or 400 larvae per container). Two feeding regimes (FR) were tested: in FR1, the amount of diet added during the experiment was based on the visually estimated larval mass present, whereas in FR2, a fixed feeding ration of 0.6 g of food per larva was applied at the start. FR1 resulted in food limitation, resulting in significantly lower body crude protein content on diet NC1 than on NC2 at larval densities 100 and 200. Larval crude fat content was higher on diets with higher nutrient concentration and at lower larval densities. For FR2, development time was shorter on diets with higher nutrient concentration and at lower larval densities. Individual larval weight and total larval yield increased with higher nutrient concentration at all four larval densities. At lower nutrient concentration, higher larval density resulted in higher individual larval weight and total larval yield, revealing an interaction between larval density and dietary quality. Larval crude protein content was higher at lower densities and lower nutrient concentration. Larval crude fat was higher at higher larval densities and nutrient concentrations. This study indicates that larval protein content is regulated within narrow limits, whereas larval crude fat content is strongly affected by nutrient concentration and by larval density.

The black soldier fly [Hermetia illucens L. (Diptera: Stratiomyidae)] can be sustainably reared on organic waste streams and thereby provide a novel animal protein source for animal feed. Black soldier fly's performance and body composition depend to a large extent on the nutrient composition of the waste stream. Black soldier fly larvae were fed on four diets consisting of vegetable by-products from the food industry. All four diets contained dried distiller's grains with solubles plus one or two other main ingredients; for diet 1 the additional ingredient was grape pulp; diet 2: potato peels; diet 3: bean seeds; and diet 4: cabbage leaves plus old bread. The diets were formulated based on an optimal summed protein and carbohydrate (P+C) concentration resulting from previous experiments and a 1:2 protein:carbohydrate (P:C) ratio. We quantified both larval and adult performance. Diet 4 was the best performing vegetable waste-based diet. In a follow-up experiment, we re-formulated diet 4 to have P:C ratios of 1:2 or 1:3 and 40 or 47% dry matter of P+C. In the first experiment, although there were differences in larval performance among the diets, all diets supported a higher larval performance than reported previously, with diet 4 having 47% P+C being the best performing diet. We infer that not only total macronutrient content but also nutritional quality of proteins and carbohydrates affected performance. In the second experiment, the two vegetable residue-based larval diets resulted in similar larval and adult performance. High dietary protein resulted in increases in larval crude fat content.

We investigate how the black soldier fly Hermetia illucens L. (Diptera: Stratiomyidae) responds to dietary protein (P) and carbohydrate (C) contents and the P:C ratio in terms of both immature and adult life‐history traits, as well as effects on larval body composition. Nine chicken‐feed based diets varying in their P:C ratio are formulated. We test three protein concentrations (10%, 17% and 24%) and three carbohydrate concentrations (35%, 45% and 55%) and their combinations. All nine diets support the complete development and reproduction of this species. Survival is high on all diets. Development time, larval yield, larval crude fat and egg yield are more influenced by P and C contents than by the P:C ratio. Low contents result in a shorter development time. Larval yield is higher on diets with higher C‐contents. Pupal development is faster on a low dietary P‐content for all three C‐contents. Egg yield only increases when P‐content increases, although it also varies with the P:C ratio. Larval crude protein content is similar on all nine diets but increases when C‐content is low (10%) in P10 and P17. Larval crude fat content is high at P24‐diets irrespective of C‐content. We conclude that a high macronutrient content combined with a low P:C ratio positively affects H. illucens performance. The diet P17:C55 supports the highest larval and adult performance and results in a high larval body protein content and an intermediate crude fat content.

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.

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.

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Fighting rural poverty in Colombia: Circular agriculture by using insects as feed in aquaculture.Wageningen Livestock Research, Report 1353. This report presents the results of a research project that investigated the opportunities to use insects produced on organic residual streams as novel protein component of fish feed to develop a circular agriculture that is environmentally, economically and socially sustainable. This was done in response to a question of the Dutch Ministry of Agriculture.