Covering 100 years of zoological research, the Handbook of Zoology represents a vast store of knowledge. Handbook of Zoology provides an in-depth treatment of the entire animal kingdom covering both invertebrates and vertebrates. It publishes comprehensive overviews on animal systematics and morphology and covers extensively further aspects like physiology, behavior, ecology and applied zoological research. Although our knowledge regarding many taxonomic groups has grown enormously over the last decades, it is still the objective of the Handbook of Zoology to be comprehensive in the sense that text and references together provide a solid basis for further research. Editors and authors seek a balance between describing species richness and diversity, explaining the importance of certain groups in a phylogenetic context and presenting a review of available knowledge and up-to-date references. New contributions to the series present the combined effort of an international team of editors and authors, entirely published in English and tailored to the needs of the international scientific community. Upcoming volumes and projects in progress include volumes on Annelida (Volumes 1-3), Bryozoa, Mammalia, Miscellaneous Invertebrates, Nannomecoptera, Neomecoptera and Strepsiptera and are followed later by fishes, reptiles and further volumes on mammals. Background The renowned German reference work Handbook of Zoology was founded in the 1920’s by Professor Willi Kukenthal in Berlin and treated the complete animal kingdom from single cell organisms to mammals in eight thematic volumes: Volume I Protozoa, Porifera, Colenteratea, Mesozoa (1925); Volume II Vermes (1933/34); Volume III Arthropoda ex. Insecta (1927/1932); Volume IV Arthropoda: Insecta; Volume V Solenogastres, Mollusca, Echinoderma (1925); Volume VI Pisces / Amphibia (1930); Volume VII Reptilia / Aves (1931); Volume VIII Mammalia. The Volumes IV Arthropoda: Insecta and VII Mammalia continued publication into the present with the most recent contributions in English language. Adapting to the accelerating speed of scientific discovery in the past decades the Handbook of Zoology entered a next phase in 2010. In the new edition of the Handbook of Zoology, the original eight thematic volumes gave way for smaller and more flexible groupings that reflect the current state of phylogenetic knowledge. All subsequent volumes were published in print as well as e-book format. The Handbook of Zoology is additionally offered as a database, the Handbook of Zoology Online, which can easily be searched and rapidly updated. Original Handbook material (ca. 28 000 pages) has been reordered along taxonomic (instead of bibliographical) categories and forms the historical basis of this Online Reference Work. As a living Online Reference, the content is continuously updated and new content added. The material can be accessed through taxonomic and subject categories as well as free text, with a diversity of linking and search options. Faster publication times through online-first publication, reference- and cross-linking, and make the Handbook of Zoology highly attractive to both authors and users.