Abstract.Five species of Calliphoridae, mostly females, were collected using fly‐traps baited with freshly killed rodent carcasses. Female blowflies were examined to determine the stages of ovarian development.The traps were selective for certain ovarian stages which varied according to the species.Phoenicia eximia(Wiedemann) was attracted to the traps mainly to oviposit, whereas females ofChrysornya albiceps(Wiedemann),C.putoria(Wiedemann) andC.megacephala(Fabricius) were captured in intermediate stages of oogenesis but seldom with eggs mature for oviposition.It is concluded that this kind of baited trap is unsuitable for the collection of male blowflies and that samples of female blowflies are specifically biased in favour of certain ovarian condition