Partial sequencing of mitochondrial DNA in the cytochrome oxidase subunit I gene of larvae, pupae, and reared adults confirmed that Asphondylia sphaera Monzen (Diptera: Cecidomyiidae) induces fruit galls on Ligustrum obtusifolium Siebold and Zuccarini, Ligustrum japonicum Thunberg, Ligustrum lucidum Aiton, and Ligustrum ovalifolium Hasskarl (Oleaceae) in Japan. In addition, part of the population of A. sphaera diverted into a short-season generation on flower buds of Rhus succedanea L. and Rhus sylvestris Siebold and Zuccarini (Anacardiaceae), and L. japonicum as short-term alternative host plants or host organs other than fruit of Ligustrum species that are the main host organs. This situation is considered to be another type of polyphagy in addition to the host alternation that has been already documented in some Asphondylia species.