Beyond the Black Box: Reproductive Strategies of the Black Soldier Fly as a Model for Bridging Evolutionary Biology...

The black soldier fly (BSF; Hermetia illucens) is rapidly emerging as a model for evolutionary biology and insect biotechnology. Although larval biology has been extensively characterised, the reproductive biology of adults remains comparatively understudied. In this review, we synthesise the most recent empirical work on physiology, behavioural and chemical ecology to open the 'black box' of BSF reproduction, focusing on processes that span eclosion to senescence. We highlight pre- and post-mating mechanisms that determine overall reproductive fitness: from mating latency, lekking dynamics, courtship and copulation, to sperm transfer, storage and oviposition. We discuss these processes within the framework of sexual selection theory. Several notable characteristics of BSF reproduction differ from traditional insect models. These include a hybrid capital-income breeding strategy (adults do not need to feed but can benefit from supplemental nutrition), protandry (early male emergence), sex-specific longevity that varies with mating status and a lek-like mating system. In addition, females possess morphologically complex sperm-storage organs, providing ample opportunity for intense post-copulatory sexual selection. Recent work shows that environmental factors such as light, humidity, temperature, substrate volatiles and rearing design strongly influence reproductive output in industrial settings, highlighting the potential for BSF to bridge fundamental and applied research. We propose a novel conceptual framework that integrates these elements and outline key unresolved questions (e.g., mechanisms of sperm precedence, female control of fertilization, reproductive barriers, drivers of speciation etc.). This interdisciplinary model supports both fundamental insights into the evolution of reproductive traits and provides practical improvements for optimizing industrial mass-rearing.