Both Prismatocerus and Tagus were reduced to subgenera or species-groups within Homoeocerus Burmeister, 1835 by Stål (1873a: 57-63). Recently, Linnavuori (1978: 14 and 1989a: 14) has used Prismatocerus as a full genus including Tagus productus Stål, the type species of Tagus Stål, implying the generic synonymy.