Supplementary descriptions of an infrequently encountered species Novophytoptus stipae Keifer 1962 (Eriophyoidea, Phytoptidae) from Achnatherum speciosum (Poaceae) based on topotypes recovered from dry plant material from California is given. Comparison of topotypes of N. stipae with fresh Novophytoptus mites from Juncus tenuis and J. balticus (Juncaceae) collected in West Virginia and Ohio failed to reveal distinct morphological differences sufficient enough to establish new taxa. All studied mites are considered belonging to one species, N. stipae. This is putatively an example of polyphagous eriophyoid species inhabiting phylogenetically remote hosts. Remarks on polyphagy and dispersal modes in eriophyoids are addressed. Uncommon features of the gnathosoma and the anal region of novophytoptines were discovered under LT-SEM. These findings emphasize peculiarities of novophytoptines in relation to their endoparasitic life style and underline numerous gaps in our knowledge on anatomy and functioning of the organism of eriophyoid mites.