Polarized skylight orientation in the desert antCataglyphis

Summary The desert antCataglyphis bicolor is able to use the pattern of polarized light in the sky as compass. By confronting the ant to single spots of artificially and naturally polarized light it is shown howCataglyphis uses the polarization pattern.When exposed to a horizontal e-vector,Cataglyphis was always oriented correctly. Orientation errors occurred, however, when other e-vector directions were presented. This indicates that the e-vector positions assumed by the ant do not coincide with the e-vector positions actually realized in the sky. From this it is concluded thatCataglyphis has no detailed knowledge of the actual azimuthal positions of the e-vectors. Instead, it is relying on a simplified celestial map of the polarization patterns in the sky (Fig. 7).Usually, the ant did not confuse celestial spots with identical e-vector directions. Even at sunset when the polarization pattern is completely ambiguous, correct orientation occurred. This suggests that the ant uses additional celestial cues such as the degree of polarization, the color or the intensity to find its way home when the sun is obscured.