Technical Abstract: Systematics is the science that identifies and characterizes all organisms i.e. the study of biological diversity. Without accurate systematic knowledge, it is not possible to determine how organisms will function especially when introduced into new habitats such as in biological pest control. The kinds of organisms used most successfully in biological control are insects and fungi, the 'megadiverse' groups of organisms about which relatively little is known. This article reviews the importance of systematics in biological pest control including the consequences of inadequate systematic knowledge. The methods used for the identification of fungi and insects are presented along with major literature references. At a time when the need for systematic knowledge is increasing, the number of scientists with this expertise is declining. At the same time, the field of systematics is advancing due increased application of molecular tools and use of the internet for interactive identification systems