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The Australian desert ant Melophorus bagoti shows remarkable visual navigational skills relying on visual rather than on chemical cues during their foraging trips. M. bagoti ants travel individually through a visually cluttered environment guided by landmarks as well as by path integration. An examination of their visual system is hence of special interest and we address this here. Workers exhibit distinct size polymorphism and their eye and ocelli size increases with head size. The ants possess typical apposition eyes with about 420-590 ommatidia per eye, a horizontal visual field of approximately 150 and facet lens diameters between 8 and 19 pm, depending on body size, with frontal facets being largest. The average interommatidial angle Delta phi is 3.7 degrees, the average acceptance angle of the rhabdom Delta rho(rh) is 2.9 degrees, with average rhabdom diameter of 1.6 mu m and the average lens blur at half-width Delta rho(l) is 2.3 degrees. With a Delta rho(rh)/Delta phi ratio of much less than 2, the eyes undersample the visual scene but provide high contrast, and surprising detail of the landmark panorama that has been shown to be used for navigation. (C) 2010 Elsevier Ltd. All rights reserved.