Psyllid. Coloured scanning electron micrograph (SEM) of the abdomen of a female psyllid (Cacopsylla pyricola). Psyllids, also known as jumping plant lice, are sap-sucking insects that are a major agricultural and garden pest. As species tend to be host specific psyllids can be used as a form of biological control for invasive plant species. Magnification: x125 when printed at 10 centimetres wide.