Quasigraptocleptes maracristinae gen. nov., sp. nov. (Hemiptera, Heteroptera, Reduviidae, Harpactorinae, Harpactorini) is described based on male and female specimens from Brazil. Photographs and comments about the syntypes of Myocoris nigriceps Burmeister, 1835, Myocoris nugax Stål, 1872, Myocoris tipuliformis Burmeister, 1838 and Xystonnytus ichneumoneus (Fabricius, 1803) are presented. The intra-specific variability and sexual dimorphic characteristics among specimens of Q. maracristinae sp. nov. are recorded. General characteristics of Hiranetis Spinola, 1837, Graptocleptes Stål, 1866, Quasigraptocleptes gen. nov. and Parahiranetis Gil-Santana, 2015, which seem to be closer genera, are compared, including those of the male genitalia of some species. A key to the species of Myocoris Burmeister, 1835, and an updated key to Neotropical wasp-mimicking Harpactorini genera are provided.