This paper provides a detailed description of Phyllocoptes adalius, eriophyoid species with a complex life cycle. P. adalius has recently become one of the most important mite pests in greenhouse rose production. We present morphometric data and illustrations that help to distinguish protogyne and deutogyne female forms. Both forms are differentiated by qualitative morphological traits such as ornamentation of the prodorsal shield and shape of microtubercles on the dorsal annuli.