Male courtship behaviour and potential for female mate choice in the black soldier fly Hermetia illucens L. (Diptera: Stratiomyidae)

The black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae) is a promising species used as protein source for aquaculture and zootechnical diets, which has been also proposed as biological tool for managing organic wastes. Here, we investigated the courtship and mating behaviour of H. illucens, recording the behavioural sequences displayed, the occurrence of same-sex interactions and the role of female-borne signals eliciting male courtship. The sequence of events leading to successful copulation is not dissimilar from other stratiomyid species, although H. illucens females were able to convey their preferences for mates according to male courtship behaviours. Males performed wing fanning during courtship prior to move backwards on the female body. Once the males mounted the females, they tapped the female abdomen with the tarsi of its second and third pairs of legs and attempted to accomplish preliminary genital contacts. Male wing fanning during mounting attempts seemed pivotal for female acceptance. Same-sex courtship behaviours were observed among males, which were not able to distinguish between males and females during the in-flight approach and the mounting attempt. Wing fanning played a key role also in evoking behavioural responses of males. Indeed, the males just approached conspecifics beating their wings during flight, while no courtship was recorded toward females that did not perform wing beating. This study improves the knowledge about sexual behaviour of H. illucens, highlighting the role of wing fanning among the range of sensory modalities used in the sexual communication of stratiomyid flies.