Two-Photon Image of Robber Fly Head (IMAGE) University of Cambridge Caption This is a two-photon image of the Holcocephala head showing the enlarged frontal facets. Using this method, the authors showed that the extremely high resolution acquired by this animal is a few (~20) large optical units. Credit Sam Fabian Usage Restrictions With credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.