Meeting Abstract
Insects often have refined color and polarization vision, however their compound eyes have poor visual acuity because the small lens of individual ommatidia are diffraction-limited. In contrast, the camera-type eyes of vertebrates do not suffer from diffraction to the same degree because they have larger apertures; the net result is diurnal vertebrates often have visual acuities that are orders of magnitude finer than insects. While many studies have discussed the role of color and polarization in private communication channels, none have examined if signals exploit the evolutionary constraint on visual acuity in the compound eyes of insects. Here we examine if warning signals —especially in species that prey on insects — have spatial characteristics that are obvious to their potential predators (e.g. birds) but not to their insect prey. We model the appearance of three types of signals to both birds and insects: 1) warning signals from species that prey on insects, 2) warning signals from species that do not prey on insects, and 3) intraspecific signals between insects. Because compound eyes are diffraction-limited, evolving a compound eye with visual acuity comparable to that provided by the camera-type eyes of diurnal vertebrates would require huge changes in lens size, and therefore physically unlikely changes in eye size. We suggest that taxon-specific constraints on visual acuity are in certain cases more rigid than constraints on color discrimination (which can change with a single amino acid substitution), making them a more reliable way to achieve private communication when the signaler would suffer from detection by insects.
