Abstract
This book contains 20 chapters, divided into 6 sections. The first section discusses the development of quality control for natural enemies. The second section consists of chapters dealing with background information on sources of variation in foraging behaviour that are regularly encountered, but not understood and often misinterpreted in mass rearing. The third section focuses on how to cope with this variation. The fourth section gives an overview of the species of natural enemies that are mass produced worldwide. The fifth section contains chapters that describe developments towards quality control testing of natural enemies. The sixth and the final section deals with actual quality control tests. This section provides a description of the guidelines that are currently used for quality control of commercially produced natural enemies, and discusses future improvements of these guidelines.