Dimorphic Sessile Apterae of the Aphid Neothoracaphis glaucae (Hemiptera) on the Evergreen Oak Quercus glauca

Species of the aphid genus Neothoracaphis (Hormaphidinae, Nipponaphidini) produce tiny, sessile, sclerotized apterous adults on leaves of oaks. Among Japanese species, "N. glaucae" has been known to have the largest, ovate apterae, while "N. saramaoensis" has smaller, elongated oval apterae on Quercus glauca. Through examining mitochondrial DNA sequences of Japanese Neothoracaphis species, we found that the two are the same species with a clear dimorphism. Neothoracaphis glaucae (Takahashi) was adopted as the valid name for the species. In Tokyo, Japan, apterae of the smaller type are abundantly seen throughout the year, and those of the larger type are generally few in number from summer to autumn. Alates, which are supposed to be sexuparae, appear from November to January. Nymphs developing into the alates are covered with long, semitransparent, bristle-like wax filaments. We conclude that N. querciphaga, N. elongata, and N. yanonis are distinct species and that both the genus Neothoracaphis and the three Neothoracaphis species other than N. yanonis form monophyletic groups among Japanese Nipponaphidini species we have examined.