Visual field structure in the Empress Leilia, Asterocampa leilia (Lepidoptera, Nymphalidae): dimensions and regional variation in acuity
We experimentally investigated proximate factors in uencing the visual detection of ying conspeci cs by male butter ies (Asterocampa leilia) engaged in a sit-and-wait matesearching tactic. Model butter ies were presented to perched males in the eld using an apparatus that permitted us to control the path and speed of a model while varying minimum distance of the model from the male, height of the model above the ground, and model size. The dependent variable in all cases was whether or not the male left his perch and pursued the model. Males responded to normal-size models up to but not beyond distances of 3 m, and, because doubling the model surface area increased the distance at which males responded, we conclude that males do not detect conspeci cs if they are more than 3 m away. At distances of 2 m or less males perched on the ground were more likely to detect conspeci cs than males perched off the ground. This is likely to be due to differences either in the background against which the perched male typically views conspeci cs or how large an angle conspeci cs subtend from a perched male’s perspective. These results suggest that thermally-driven changes during the activity period in perch preferences have consequences for success in mate detection that may be evolutionarily signi cant.