A window into fly sex: mating increases female but reduces male longevity in black soldier flies

Sexual reproduction increases genetic diversity but it is also associated with costs such as exposure to parasites or reduced lifespan. Black soldier flies, Hermetia illucens (Linnaeus 1758), are a suitable model to investigate the trade-offs between reproduction and longevity as they largely rely on their larval resources and do not have to intake nutrients as adults. Here, we investigate the influence of mating status on adult longevity. We found that females have shorter longevity than males, but the inter-sexual difference in lifespan is reduced through mating which increases female but decreases male longevity. This suggests cost in males whilst female longevity is increased, likely via nutrients transferred by males during copulation (sensu nuptial gifts). This study also presents an investigation of the transparent abdominal ‘window’ of adult black soldier flies, of which the fullness may be a proxy for both age and mating status.