Carboxylic acids from hairpencils of male Amauris butterflies (Lep.: Danainae).

63 Carboxylic acids were identified from the male hairpencils of four species of the genus Amauris (Lep.: Danainae), namely A. echeria (Stoll), A. hecate (Butler), A. ochlea (Boisduval) and A. albimaculata Butler. Straight chain saturated as well as unsaturated carboxylic acids, some of which containing an additional oxygen function, contribute to the species-specificity of the odour bouquets. Oxygenated fatty acids form a new class of insect volatiles, 5 of the 10 ketoacids found represent new natural products. (E)-7-Oxo-11-tetradecenoic acid is the main volatile component of the hairpencils of A. echeria, the species with the highest amount of oxygenated fatty acids (70% of the extractable volatiles). 9-Hydroxyoctadecanoic acid is a major compound in both A. ochlea and A. albimaculata while in A. hecate oxygenated carboxylic acids are present in minute amounts only.