This paper reviews major results of taxonomical studies on Japanese species of harvestmen made by me over the past 40 years. The first attempt as a postgraduate student was to provide precise species identification of all-female populations of the curvipalpe-group of Leiobunum (Eupnoi: Sclerosomatidae) in Hokkaido. It was confirmed that they were Leiobunum manubriatum and L. globosum and they were facultative thelytokes showing typical patterns of geographic parthenogenesis. Leibunum manubriatum consisted of diploid populations with 2n=24 and tetraploid populations with 2n=ca. 48, while L. globosum was a tetraploid species with 2n=ca. 48. Population genomics analyses recently made revealed that L. globosum originated from tetraploid populations of L. manubriatum, thus L. manubriatum is paraphyletic. Most of the Japanese species of Opiliones having wide distributional ranges are polytypic and consist of many geographic races that intergrade one another by making hybrid zones where they meet. Some topics for those species revealed by cytogenetical analyses are briefly reviewed. They include chromosomal hybrid zones in several species, two cases of circular overlap in Gagrellula ferruginea, and B–chromosomes in Psathyropus tenuipes.