Today, most biologists would agree that there is no objective criterion to determine the rank of a supraspecific taxon. As a result, comparing how many species different taxa of the same rank include does not make much sense. Yet we keep doing it. Following that tradition we may ask a question: What is the largest genus, i.e. what genus includes the largest number of species? Even if we do not know the answer, we might consider the well-established fact: life on Earth, as we know it, is represented mostly by beetles. Then it is highly likely that the largest genus is a member of Coleoptera. Indeed, this is the case, and the largest animal genus belongs to rove beetle. The genus Stenus is the champion and includes about 3000 fantastic species, each more beautiful than the next.

One of my favorite papers published in 2022 is the long awaited final part of the monograph on Stenus of Japan by Dr Shun-Ichiro Naomi and colleagues (The subfamily Steninae Macleay, 1825 (Coleoptera: Staphylinidae) of Japan. Part 3. Stenus satsuki-group and S. cephalotes-group. National Museum of Nature and Science Monographs No. 53, ISSN 1881-9109). The book completes the revision of the Japanese species of Stenus, a result of a forty year long study of the genus. Now all the 340 Japanese species of Stenus have been illustrated and included in identification keys. Of course, all good works on Stenus include descriptions of species new to science. Dr Naomi’s book is no exception and adds seventeen more species to the genus. With this remarkable guide in hands, an entomological excursion to Japan seems inevitable.