Scale insect. Coloured scanning electron micrograph (SEM) of a scale insect (superfamily Coccoidea) on a leaf. This pest feeds on the plants sap. It secretes a powdery wax coating that protects it against pesticides and predators. Many scale species are serious crop pests and are particularly problematic for their ability to evade quarantine measures. Magnification: x150 when printed at 10 centimetres wide.