Behaviour 2019
The Sexually Dimorphic Eyes of a Band-winged Grasshopper: Females See Finer Details
Nicholas Brandley, Sara Garcia. College of Wooster, Wooster, OH, United States

Behaviors are limited by sensory systems, as animals must detect stimuli to respond. One sensory capability that limits behaviors is visual acuity (the fineness/coarseness of vision) which varies by orders of magnitude across species. The best predictor of visual acuity is size, with larger-eyed animals having finer vision in multiple taxonomic groups. Yet surprisingly, it is unknown whether size influences visual acuity within a species, especially in sexually dimorphic species. Here we examine the visual acuity of the band-winged grasshopper Dissosteira carolina using a radius of curvature estimation. Compared to males (n=25), females (n=23) are ~20% larger and have ~12% wider and ~13% taller eyes. Visual acuity is ~15% finer in females and the total number of facets increases from ~4600 in males to ~5500 in females (n=3). Other distantly related species of band-winged grasshoppers (Arphia pseudonietana, Spharagemon equale) also have sexually dimorphic visual acuities, suggesting that vision may be dimorphic in many species. The behavioral consequences of this dimorphism --- and how often sexual size dimorphisms lead to visual dimorphisms --- remains to be studied.