The Hymenoptera is one of the largest orders of terrestrial arthropods and comprises the sawflies, wasps, ants, bees and parasitic wasps. This text examines the state of all major areas of research for this important group of insects, including systematics, biological control, behaviour, ecology, and physiological interactions between parasitoids and hosts. The material in this volume originates from papers presented at the Fourth International Hymenoptera Conference held in Canberra, Australia in early 1999.