The purpose of the present invention is to provide a mesoionic compound or a salt thereof that exhibits excellent control activity against various pests. Provided is a mesoionic compound represented by formula (1). (In the formula, Ra represents a hydrogen atom or a methyl group, R1 represents a phenyl group or pyridyl group which is optionally substituted with up to two substituents selected independently from R2, and R2 represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a c-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a methyloxy group, an ethyloxy group, an n-propyloxy group, an i-propyloxy group, a c-propyloxy group, an n-butyloxy group, an i-butyloxy group, a s-butyloxy group, a t-butyloxy group, an n-pentyloxy group, a trifluoromethyloxy group, a 2,2,2-trifluoroethyloxy group, a methylthio group, a methylsulfoxy group, a methylsulfonyl group, a vinyl group, an ethynyl group, etc.).本發明係以提供對於各種有害生物顯示更為優異之防除活性的中離子性化合物或其鹽作為目的。式(1)表示之中離子性化合物，(式中，Ra係表示氫原子或是甲基，R1係表示獨立選擇自R2以最多2個之取代基視情況取代的苯基或吡啶基，R2係表示氫原子、氟原子、氯原子、溴原子、甲基、乙基、n-丙基、i-丙基、c-丙基、n-丁基、i-丁基、s-丁基、t-丁基、氯甲基、二氯甲基、三氯甲基、甲氧基、乙氧基、n-丙氧基、i-丙氧基、c-丙氧基、n-丁氧基、i-丁氧基、s-丁氧基、t-丁氧基、n-戊氧基、三氯甲氧基、2,2,2-三氯乙氧基、甲硫基、甲基磺氧基(Methylsulphoxy)、甲基磺醯基、乙烯基、乙炔基等)。
