Parasitic wasps of the genus Scelio play an important role in the regulation of orthopteran populations and are implicated in suppressing numbers of numerous pest locusts and grasshoppers. This landmark volume provides a full taxonomic treatment of the sixty species of Scelio found on the Australian continent and reviews in detail the biology and ecology and host relationships of Scelio on a worldwide basis. Taking an international perspective, the text outlines our current knowledge on topics such as host finding, population biology, and methods and techniques for collection and study in the field. The use of Scelio as biological control agents is discussed and comprehensive checklists document the recorded host relationships of each known species worldwide. There is a full taxonomic revision of all Australian species of Scelio, half of which are newly described. Each species description is complemented with high-quality line drawings, micrographs and distribution maps. In addition, an illustrated key to species enables easy identification of species by non-taxonomists. Biology, Ecology and Systematics of Australian Scelio provides wasp taxonomists, researchers of orthoptera and biological control workers with a basis for detailed studies elsewhere on this economically important group of insects.