The comparative study of ontogeny and morphological structures of quill mite infrapopulations of a newly described species Peristerophila hirundineussp. nov. from Merops hirundineus (Coraciiformes: Meropidae), collected in Namibia, D.R. Congo, Zimbabwe, and Tanzania, shows evidence of female dimorphism in the genus PeristerophilaKethley, 1970. This proves that females of quill mite species referred to the genus Peristerophila are homeomorph forms, while those referred to the genus Castosyringophilus Bochkov and Perez, 2003 are heteromorph ones. Therefore, the genus Castosyringophilussyn. nov. is synonymized herein with the genus Peristerophila. The following new combinations for mite species formerly referred to Castosyringophilus are proposed: Peristerophila forpi (Bochkov and Perez, 2002) comb. nov., P. claravis (Skoracki and Glowska 2008) comb. nov., and P. meropis (Skoracki, Hromada and Sikora, 2017) comb. nov. The possible evolutionary sense of the female dimorphism in syringophilid mites is discussed.