Female receptivity in butterflies and moths is influenced by a multitude of factors that vary between virgin and mated females, and is often affected by the quality and persistence of courting males. Mated females of polyandrous species frequently display a period of non-receptivity following mating, often resulting from factors transferred by the male at mating. Some of these compounds have a transient effect (e.g. anti-aphrodisiacs and mating plugs), whereas others induce long-term suppression of receptivity (i.e. sperm and seminal factors). Sperm appear to generally induce long-term suppression of female receptivity in both butterflies and moths. In some species, production of non-fertile sperm may function to fill the female's sperm storage organ and switch off receptivity, although whether this is a general phenomenon across the Lepidoptera has not yet been examined. Examination of seminal fluids suppressing female receptivity in moths suggests that more than one factor is implicated, but frequently the transfer or stimulation of Juvenile Hormone production is involved. Surprisingly, potential seminal factors influencing female receptivity in butterflies remain largely unexplored. In this review, I summarize the various factors that are known to affect female receptivity in the Lepidoptera to date, and briefly compare the function and similarity of the Pheromone Suppressing Peptide (HezPSP) in moths to that of the Sex Peptide in Drosophila melanogaster (DrmSP). The exciting possibility that seminal peptides in the Lepidoptera and Diptera (e.g. Drosophila melanogaster) may have shared functionality is discussed.