Influence of Substrate Type, Moisture, and Compaction on Pupation and Adult Emergence of Black Soldier Fly ( <i>Hermetia illucens</i> )

ABSTRACT Pupation is a critical developmental stage for Hermetia illucens L. (Diptera: Stratiomyidae) (black soldier fly, BSF) in mass‐rearing systems, directly influencing adult emergence and reproductive output. This study evaluated six substrate types (sand, wood shavings, topsoil, vermiculite, spent larval substrate, and potting soil) to assess the effects of moisture level and compaction on pupation success, adult emergence, and mortality. Substrate performance varied according to physical properties, including dry matter content, bulk density, and water‐holding capacity. Moist substrates consistently outperformed dry ones, with optimal pupation observed at 10% moisture. Although adult emergence was highest at 40% moisture, elevated moisture levels increased the risk of mold formation in some substrates. In general, 10% moisture achieved not only high percentages of pupation and adults but also reduced mortality while avoiding the risk of mold growth. Mild compaction had no adverse effects on larval development or emergence, suggesting that moderately compacted substrates could be reused to enhance cost efficiency in production systems. Among all tested materials, spent larval substrate emerged as the most practical and economical option due to its availability and effectiveness.