Chemical Ecology, Göteborg University, Dept of Botany, Box 461, 405 30 Göteborg, Sweden.
Androconia are male pheromone releasing structures. They are often modified scales, scattered over the wing or in patches (stigma). They are found in several families within butterflies (Lepidoptera). The pheromone mechanism seems to be different in each group but is often species specific and acts as species recognition. Scent scale substances of three Hesperidae species, (Hesperia comma, Ochlodes faunes and Thymelicus lineola) were examined. These three species have visible stigma which has proved to contain pheromones. The stigma was extracted with pentane. All chemical analyses were made by GC-MS. The results showed that each pheromone was comprised of 3 to 4 volatile compounds: H. comma; p-cresol, trimethoxybenzene, 6,10,14- trimethyl - 2 - pentadecanon and hexadecatrien-1-ol O. faunes; phenol, methyl-3,7,11-trimetyl - 2,6,10 - dodecatrienoate, benzyl benzoate and etovanillon T. lineola; 6,10,14-trimethyl -2-pentadecanon, vanillin and phytol. The amount of each compound is very low, 0.3-3.5 ng, due to the specialized pheromone transport structures (osmophore). H. comma, which has the most specialized scent releasing structures, also has the smallest amount of pheromone. Scanning electron microscopy pictures of the androconia from O. faunes revealed osmophores and lysis of osmophores. As a reference species Callophrys rubi (Lycaenidae) was examined,. Their androconia consist of reduced wing scale with solid structure, instead of the hollower structure of wing scale, presumably consisting of pheromone revealing tissue. Similarities in compounds between the species, i.e.vanillin, acetovanillone and trimethoxybenzene, might reflect relationship and therefore give us a key to evolution of scent compounds.