The genus Oligonychus Berlese : taxonomic assessment and a key to subgenera, species groups, and subgroups

 A comprehensive taxonomic assessment of the most agriculturally important and highly diverse spider mite genus, Oligonychus Berlese (Acari: Tetranychidae) was performed. The sub-generic division, species groups, doubtful species, species complexes and the interpretation of a key generic character are discussed. Based on the orientation of the male aedeagus, only two subgenera, namely Oligonychus Berlese (aedeagus downturned) and Reckiella Tuttle & Baker (aedeagus upturned), are valid in the genus Oligonychus . The subgenera Homonychus Wainstein, Metatetranychoides Wainstein, and Wainsteiniella Tuttle & Baker are considered to be synonyms of the subgenus Oligonychus, whereas the subgenus Pritchardinychus Wainstein is proposed as a synonym of the subgenus Reckiella. Moreover, based on female morphological characters, four species groups (coffeae , exsiccator , iseilemae , and peruvianus ) and 11 species subgroups (aceris , biharensis , coffeae , comptus , exsiccator , gossypii , iseilemae , peruvianus , pritchardi , smithi , and subnudus ) are suggested in the subgenera Oligonychus and Reckiella . Fourteen Oligonychus species are proposed as species inquirendae, and potential cryptic species complexes in the genus Oligonychus are briefly highlighted. It is agreed that the clunal seta h[sub.1] is always absent, while the para-anal setae h[sub.2] and h[sub.3] are always present in the genus Oligonychus. A key to subgenera, species groups, and species subgroups of the genus Oligonychus is provided. Keywords: Morphology, species complex, species identification, species inquirenda, spider mite, taxonomy