Subalpine sclerophyllous oak forest grows at high elevation in Taiwan, distantly separated from similar forest communities found in western China, Tibet and India. An investigation on bud‐breaking phenology of oaks and associated phytophagous insects in this community revealed an undescribed species of Teratozephyrus lycaenid. This and other oak‐associated insects suggest that the presence of this oak community in Taiwan resulted from a more widely distributed community. The newly discovered Teratozephyrus turned out to be most closely related to T. nuwaii, described from western China, and is described below as T. elatus sp. nov. Two other species of Teratozephyrus also inhabit Taiwan, but both are associated with broad‐leaved oak forests. Of them, T. arisanus is widespread both in China and Taiwan, is morphologically distinct from the other Teratozephyrus species and is exclusively associated with broad‐leaved oaks. The other, T. yugaii, probably gained its broad‐leaved oak association secondarily as no...