Male sex pheromone components in the butterfly Heliconius

10 Sex specific pheromones are known to play an important role in butterfly courtship, and may 11 influence both individual reproductive success and reproductive isolation between species. 12 Extensive ecological, behavioural and genetic studies of Heliconius butterflies have made a 13 substantial contribution to our understanding of speciation. However, although long suspected 14 to play an important role, chemical signals have received relatively little attention in this 15 genus. Here, we combine morphological, chemical and behavioural analyses of a male 16 pheromone in the neotropical butterfly Heliconius melpomene. First we identify specialized 17 brush-like scales that are putative androconia, and lie within the shiny grey region found on 18 the hindwing of males. We then describe six putative male sex pheromone compounds, which 19 are largely confined to the androconial region of the hindwing of mature males, but not 20 immature males or females. Finally, behavioural assays reveal subtle, but detectable, 21 differences in female response to models scented with hindwing androconial extracts of 22 mature conspecific males as compared to unscented controls. Collectively, the results describe 23 structures involved in release of the pheromone and a list of potential male sex pheromone 24 compounds triggering a behavioural response in females. 27 28 29. CC-BY 4.0 International license not peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was .