Response to volatiles from decaying organic matters and behavioural plasticity in male and female Hermetia illucens

Despite its importance in the circular economy and the large amount of research published each year on this insect, the chemical ecology of adult Black Soldier Fly (BSF), Hermetia illucens, remains poorly understood. Only a few studies have described antennal olfactory sensilla and the ability of both sexes to detect chemicals associated with organic decomposition. In this context, the present study aims to deepen our understanding of the sensitivity of male and female BSF antennal sensilla to olfactory cues from decaying organic matter, its plasticity throughout the adult lifespan, and its potential role in reproduction. This is achieved by: (i) single sensillum recordings (SSR) targeting olfactory sensory neurons (OSNs) housed in different olfactory sensilla stimulated with volatiles from decaying substrates; and (ii) Y-tube olfactometer bioassays, to assess the attractiveness of these cues to males and females differing in age and reproductive status. Different antennal sensilla respond similarly in both sexes to VOCs emitted by decaying substrates. These cues elicit sex- and stage-specific taxis: males are always repelled, whereas females are repelled after emergence but become attracted upon reaching sexual maturity, when they need to oviposit. These findings suggest that the tested olfactory cues could drive sexand stage-specific movements of H. illucens adults, relative to their emergence, mating and oviposition sites. This knowledge advances our understanding of BSF chemical ecology and should be considered for the optimisation of rearing systems to improve industrial productivity