Nippolachnus is a small Palaearctic-Oriental genus of very characteristic aphids that live on the leaves of woody Rosaceae. One species, N. piri, has hitherto been regarded to be widely distributed and relatively polyphagous. Members of this genus are considered to be easy to recognize due to the absence of the ocular tubercle and triommatidia on the head. We conducted research on the morphology and generic characters of Nippolachnus piri complex using scanning electron microscopy (for the first time) and DNA barcoding. We analyzed N. piri populations on Pyrus and other plants (Eriobotrya, Rhaphiolepis and Sorbus) in Japan and the Republic of Korea. Specifically, a high genetic divergence value was found between the N. piri populations associated with different host plants. SEM investigation of the head capsule revealed that a triommatidium is present under the compound eye, despite their lack of an ocular tubercle. We propose Nippolachnus micromeli Shinji, 1924 stat. nov. as a cryptic species in the N. piri complex based on a morphological comparison, DNA barcoding and different host-plant associations. Illustrations and descriptions of studied species are given. Morphological keys to the apterae and alatae of all known species of the genus Nippolachnus are also provided.