Black Soldier Fly Reproduction under Different Adult Densities and Light Regimes

The black soldier fly (BSF) <i>Hermetia illucens</i> L. (Diptera: Stratiomyidae) has been recognised as a promising insect species for sustainable management of organic waste and by-products. Indoor breeding of BSF with artificial lighting has been proved successful, but efforts are still needed to efficiently maximise BSF indoors’ reproductive output. Increasing adult density seems a viable option to exploit the limited space constraint under indoor breeding, whereas decreasing artificial lighting duration may reduce unnecessary power consumption. This study aimed at investigating the effects of adult density (370, 926, and 1852 pairs/m³), light regime (8L : 16D, 12L : 12D, and 16L : 8D), and their possible interactions, on some BSF life history traits that are relevant to BSF reproduction. The results show that the overall BSF reproductive output increased with increasing adult density, but was not affected by light regime <i>per se</i>. With a BSF adult density of 1852 pairs/m³, a hatchling production of 7.5 × 10⁵/m³ was achieved within 10 days. At the highest adult density, increasing photoperiod increased hatchling production, but also decreased the number of hatchlings per watt used for artificial illumination. The temporal oviposition patterns, individual female reproductive output, mating success, egg hatching rate, and insect survival rate were not significantly affected by adult density or light regime as simple effects. However, the interaction between adult density and light regime was significant for the first oviposition peak, individual female reproductive output, and insect survival rate. The possible mechanisms behind our results are discussed.