Remarkable Species Diversity of the Leafhopper Genus Xestocephalus (Hemiptera: Cicadellidae: Aphrodinae) in Thailand

Simple Summary Thailand, a country on the Indochinese peninsula in Southeast Asia, is part of a biodiversity hot spot that harbors a large number of endemic species. The insect fauna remains poorly known, but a recent bioinventory has provided many new specimens for study. We review the common, widespread leafhopper genus Xestocephalus from Thailand and provide detailed morphological descriptions (the main evidence distinguishing species) and distributions of all species. Seventeen species were recognized, including twelve new species and four species recorded in Thailand for the first time. Xestocephalus Van Duzee is among the most common and widespread genera of Cicadellidae in the temperate and tropical regions of the world. In the present study, 205 specimens of the genus Xestocephalus were collected in Thailand, whereas only a single species of the genus was recorded previously using Malaise trap field sampling, studied by comparative morphology. Seventeen species were recognized, including twelve new species: X. binarius sp. nov., X. chrysanthemum sp. nov., X. cowboyocreus sp. nov., X. densprint sp. nov., X. dimiprocessus sp. nov., X. exproiecturus sp. nov., X. gracilus sp. nov., X. limpidissimus sp. nov., X. malleus sp. nov., X. nonattribus sp. nov., X. recipinams sp. nov., and X. tenusis Liang sp. nov. Four species were recorded in Thailand for the first time: Xestocephalus abyssinicus Heller and Linnavuori, Xestocephalus asper Linnavuori, Xestocephalus ishidae Matsumura, and Xestocephalus toroensis Matsumura. Detailed morphological descriptions of all 17 species are given; photographs of external habitus and male genitalia of the species from Thailand are provided. A checklist of species of the genus is also given, and a key to all Thailand Xestocephalus species is also provided.