Ocellus (simple eye) of a European Hornet (Vespa crabro). A Hornet has three ocelli on top of its head, the front central ocellus shown here is termed the median ocellus. The ocelli don't capture a focussed image, instead acting as simpler photoreceptors, probably aiding orientation when flying and detecting sudden changes in light levels. Sherwood Forest, Nottinghamshire, UK. November. x70 life size when printed at 10cm across. Focus stacked image.