Fig. 6. Visual properties of the landmarks used during experiment 2. The optical properties have been determined following Kollmeier (Kollmeier, 2005) by measuring the remission properties under natural (sunlight) conditions at the specific wavelengths of the ant's light receptors (absorption maxima: green 500 nm, bandwidth 90 nm; UV 350 nm, bandwidth, 60 nm). The optical properties of the landmarks are predominantly defined by the paint used and not by the surface roughness.