The cicada Hyalessa maculaticollis is widely distributed in East Asia, and is noted for its great morphological variability. The variation in this species and its allies has been a long-standing controversy. The population differentiation, genetic structure and phylogeography of this species are explored based on morphological observations, mitochondrial and nuclear DNA analyses, and comparison of the calling song structure of males. Our results reveal that the abundant intraspecific morphological variations are consistent with high levels of genetic divergence in this species, but incongruence between the morphological variations and genetic divergence is found in a few lineages. Phylogenetic and network analyses indicate that H. maculaticollis is composed of two major lineages -China and Japan. The East China Sea (ECS) land bridge acted as a dispersal corridor for H. maculaticollis during the glacial period. The climatic oscillations in the Pleistocene and the terrain structure of East Asia influenced population differentiation. The divergence time between the two sides of the East China Sea is estimated to be ∼1.05 (95% CI = 0.80-1.30) Ma, which was about the same period during which the sea level increased rapidly during the 'Ryukyu Coral Sea Stage' (0.2-1.3 Ma). Populations of H. maculaticollis are structured phylogeographically, with the China populations differentiated into a greater number of highly structured haplogroups. Qinling Mountains and the mountainous regions around the Sichuan Basin are presumed to have been major refugia for H. maculaticollis in glacial periods, and a recent population expansion has been detected for populations distributed in the area to the north of Qinling Mountains. The high degree of haplotype and nucleotide diversity shown in East China populations suggests that the flat terrain with low-altitude hills are suitable for the survival of H. maculaticollis. The species H. fuscata, treated as an independent species from H. maculaticollis by some researchers based on acoustic analyses of the calling song structure, is confirmed to be a junior synonym of H. maculaticollis based on the results of our analyses of morphological variation, calling song structure and acoustic playback experiments. Past geological events and climatic oscillations have played important roles in forming the contemporary genetic diversity Correspondence: Cong Wei, Key Laboratory of Plant Protection Resources and Pest Management, Ministry of Education, Entomological Museum,

One new species of the genus Hyalessa China, H. wangi sp. nov., from Yunnan, China is described. Partial mitochondrial COI gene (DNA barcoding) of this new species is sequenced and uploaded to GenBank. A key to all species of Hyalessa is provided.