Morphological and chemical analysis of male scent organs in the butterfly genus Pyrgus (Lepidoptera: Hesperiidae)

Chemical communication in the family Hesperiidae (Lepidoptera) is practically unstudied, even though this group includes approximately 4,000 species and represents a fifth of the world's butterfly fauna. We present the first comparative morphological and chemical analysis of scent organs for nine species in the genus Pyrgus, the most species-rich hesperiid genus in the Palearctic region. Our results show that the morphology of the two main male scent organs-the costal fold and the tibial tufts-does not differ between species. The chemical analyses detected a total of 125 different compounds exclusively present in these organs. We document great interspecific differences and much narrower intraspecific variability in the chemical profiles. The dynamics of chemical versus genetic distances indicate two different phases: a faster (but more variable) initial chemical divergence at lower genetic divergences (probably related to speciation) and a slower but more constant differentiation (drift). As a result most species can be identified based on their chemical profiles, except for a closely related species pair (P. malvae/P. malvoides) for which hybridisation is common in the contact zone. Our results suggest that the Hesperiidae is a group with great potential for the study of chemical communication that deserves further attention.