We determined the optical axes of ommatidia in the wild-type female blow¯y Calliphora by inspecting the deep pseudopupil in large parts of the compound eye. The resulting map of optical axes allowed us to evaluate the spatial resolution in di erent parts of the eye in terms of interommatidial angles as well as the density of optical axes, and to estimate the orientation of ommatidial rows along the hexagonal eye lattice. The optical axes are not homogeneously distributed over the eye. In the frontal visual ®eld the spatial resolution is about two times higher than in its lateral part and about three times higher as compared to the eye's dorsal pole region. The orientation of the ommatidial rows along the eye lattice is not the same for di erent regions of the eye but changes in a characteristic way. The inter-individual variability in the orientation of the ommatidial rows is estimated to be smaller than 8°. The characteristic arrangement of the ommatidial lattice is discussed as an adaptation for e cient evaluation of optic¯ow as induced during self-motions of the animal.