sperm and seminal fluid proteomes of the field cricket teleogryllus oceanicus identification of novel proteins transferred to females at mating reproductive proteins are amongst the most evolutionarily divergent proteins known and research on genetically wellcharacterized species suggests that postcopulatory sexual selection might be important in their evolution however we lack the taxonomic breadth of information on reproductive proteins that is required to determine the general importance of sexual selection for their evolution we used transcriptome sequencing and proteomics to characterize the sperm and seminal fluid proteins of a cricket teleogryllus oceanicus that has been widely used in the study of postcopulatory sexual selection we identified 57 proteins from the sperm of these crickets many of these had predicted function in glycolysis and metabolism or were structural and had sequence similarity to sperm proteins found across taxa ranging from flies to humans we identified 21 seminal fluid proteins some of which resemble those found to be involved in postmating changes to female reproduction in other species some 27 of sperm proteins and 48 of seminal fluid proteins were of unknown function the characterization of seminal fluid proteins in this species will allow us to explore their adaptive significance and to contribute comparative data that will facilitate a general appreciation of the evolution of reproductive proteins within and among animal taxa