A sexual dimorphism in the spatial vision of North American band-winged grasshoppers

Visual acuity (VA) --- a measurement of the fineness or coarseness of vision --- may vary within a species including between the biological sexes. Although numerous studies have found males with finer VA than females, relatively few have shown the opposite with females having finer vision. This is surprising because our understanding of between species differences in VA suggests that females may have finer vision than males if they 1) are larger than males, or 2) need finer vision to detect and/or discriminate between males. Here, we estimate the interommatidial angle (∆Φ, an anatomical measurement of VA) in three species of band-winged grasshoppers in which females are both the larger sex and likely interpret visual signals (Arphia pseudonietana, Dissosteira carolina, and Spharagemon equale; total n = 98). Using a radius of curvature estimation method, we find that females have ~19% finer estimated ∆Φ than males in the most acute region and axis of the eye, but that this dimorphism var...