Sexually Dimorphic Visual Processing in the Yellow-Fever Mosquito, Aedes aegypti

Abstract

Flying insects process motion across the visual scene to regulate their ground speed, correct course deviations, and behaviorally relevant stimuli such as avoiding predators or finding hosts. The yellow-fever mosquito Aedes aegypti provides a useful model for studying these visually guided behaviors, as both sexes use vision to track moving features. Approaching a moving target presents mosquitoes with a demanding visual problem: they must extract target motion from the changing visual scene while simultaneously controlling their own flight and responding to potentially dangerous movements. To understand this, we first studied free-flight responses to static and moving vertical targets in a wind tunnel system capable of projecting dynamic visual stimuli, and found that males and females are sexually dimorphic with respect to their responses to target motion. When the feature was static, both males and females advanced toward it during flight; however, when it oscillated laterally at 2 Hz, only females continued to pursue it. In a subsequent yaw-unrestrained magnetic tethering paradigm, we showed that this divergence cannot be simply explained by sex-specific differences in visuomotor tuning dynamics, while micro-CT reconstructions revealed only modest sexual differences in eye morphology and broadly similar patterns of estimated spatial acuity. Together, these results indicate that males retain the biomechanical capacity to track oscillating targets but actively suppress approach behavior during free flight, whereas females pursue salient features independently of target motion. This pattern aligns with sex-divergent visual ecologies because the risk of approaching a large moving feature too closely likely outweighs the benefits for males seeking mates, whereas for host-seeking females the reproductive necessity of blood feeding overrides this avoidance.