Pupation substrate and prepupal handling affect eclosion rate, timing, and adult morphology in black soldier flies (Hermetia illucens; Diptera: Stratiomyidae)

Abstract

On farms, the conditions experienced by black soldier fly (BSF) prepupae may impact their development and survival, altering production goals by changing the fitness of breeding adults. Few studies have addressed the impact of environmental variables (such as substrate type or moisture content), or stressors like handling, on the development and survival of BSF as they transition from prepupae through adulthood. This study examined the effects of pupation substrate (corn cob grits, potting soil, vermiculite, wood chips, and frass), moisture content (20%, 60%, and 100%), and handling during the prepupal period (daily handling, no handling) on eclosion rate and timing, morphology (mass, head width, thorax length), and abdominal window fullness of adult BSF. Handling delayed adult emergence by over three days, reduced eclosion rates by 30.6%, reduced head width and wet mass in adult males, and reduced window fullness and head width in adult females. Frass resulted in the lowest eclosion rate (72.1 {+/-} 2.4%) while corn cob grits (82.2 {+/-} 2.3%) and wood chips (81.5 {+/-} 2.2%) had the highest. Wood chips also resulted in the highest wet and dry mass, head width, and thorax length for adult males and females. Wood chips may be the best pupation substrate for BSF as it enhances body size and has a good eclosion rate. Significant prepupal handling delays adult emergence, reduces eclosion/survival rates, and reduces adult body size; however, more research is necessary to determine if the less chronic handling regimes that are likely present on farms produce similar effects.