Ultrastructure of the black soldier fly antennal sensilla (Hermetia illucens, Stratiomyidae: Hermetinae)

: Every year, more than two hundred billion individuals of the black soldier fly Hermetia illucens are reared on an industrial scale to convert a wide range of organic by-products into high-value materials for agricultural and industrial applications. The present ultrastructural investigation, using scanning (SEM) and transmission (TEM) electron microscopy, describes the fine morphology of antennal sensilla in males and females: three types of olfactory sensilla (two multiporous and one coeloconic), one type of uniporous grooved sensillum chaeticum with gustatory and mechanosensory functions, and one type of small peg sensillum with a probable hygroreceptive function. In addition, pseudo-lamellate sensory neurons, not connected to the cuticle, are described in the last two flagellar segments, which otherwise lack sensilla. These findings provide essential groundwork for future electrophysiological and behavioral investigations to deepen the knowledge on H. illucens sensory biology, which may contribute to optimizing global mass-rearing systems. Moreover, the results, together with hypotheses on the function of the paddle-like last flagellomere, may be relevant for exploring the evolutionary differentiation of the ancestral Dipteran flagellum into the complex sensory system characteristic of the Brachycera.