Impacts of stress on production of volatile organic compounds in the black soldier fly, Hermetia illucens (Linnaeus) (Diptera: Stratiomyidae)

The black soldier fly (BSF) is the “crown jewel” of insect agriculture as its larvae can transform organic waste streams into valuable resources, like animal feed, fertilizer, and biofuels. However, mass production of BSF often introduces suboptimal conditions leading to increased stress and decreased yield. Therefore, we aimed to investigate the impact of two specific stressors (crowding and heavy metal exposure) on the volatile organic compounds (VOCs) produced by BSF. Neonate larvae were placed on chicken feed at 10,000 (low density, LD) or 20,000 larvae/kg diet (high density, HD) for four days. Three replicates of 1,000 larvae from each density treatment were placed on 1 kg of control feed or feed inoculated with 500 (low zinc, LZ) or 2,000 mg/L (high zinc, HZ) zinc sulfate heptahydrate, and allowed to develop for seven days at 30°C, 70% RH, and 12:12 L:D. Collection of VOCs was performed with activated charcoal strips hung ~5 cm above the feeding substrate, which subsequently underwent GC-MS. Principle components analysis revealed differentiation of VOCs among density treatments, though no distinction of VOCs was observed among zinc treatments. Though further statistical analysis is required to identify and quantify novel VOCs, preliminary results indicate that eicosane, hexadecane, and tetramethyl pyrazine were strongly associated with LD, whereas mostly ester compounds (e.g., Hexadecanoic acid trimethylsilyl ester) were associated with HD treatments. Our results indicate the need for further exploration of stress-associated VOCs in early BSF development, which will help inform best practices to minimize stress and yield loss in BSF production.