Aphids and their colonies are excellent arenas in which to observe predators in action. A range of insects come to eat or parasitise the aphids or to drink their honeydew.

As a child Graham Rotheray was intrigued by flies buzzing around his parents' vegetable garden, especially the hoverflies and their mimicking of wasps in order to evade birds. For his PhD he devised both laboratory and field experiments to investigate parasitic insects that attacked the larval stages of hoverflies. In 1980 he applied his expertise to a study of parasites of a major pest species in the eastern United States, the introduced gypsy moth, in an attempt to devise a biological means of controlling their spread. On returning to Britain, Graham was appointed Curator of Insects at the National Museums of Scotland in Edinburgh. He was charged with developing the collections of Diptera. He developed an interest in ancient Scottish woodlands and the hoverflies that occur there, such as the rare Callicera rufa.