Scanning electron micrograph of a greenfly eye. Greenflies (aphid) have a pair of compound eyes for accurate perception of movement. The small protrusion coming from the side of the eye is called an ocular tubercle which is made up of three lenses (triommatidium). Aphids are insects, many species of which are agricultural pests that feed on plant sap. Horizontal width of image is 280 micrometres. Supplied by Kevin Mackenzie, courtesy of Wellcome Images.