Purity >98%. Unsaturated, long-chain hydrocarbons are found on the cuticles of insects and can act as pheromones. In mature Drosophila melanogaster, certain cuticular hydrocarbons are sexually dimorphic: males synthesize 23- and 25-C monoenes and females produce 27- and 29-C dienes. Each of these lipids plays specific roles in regulating male sexual behavior, with dienes stimulating courtship. 7(Z),11(Z)-Pentacosadiene is a 25-C hydrocarbon that is found in low abundance on cuticles of mature Drosophila females. Depletion of a female-specific elongase (eloF), which leads to an increase in 7(Z),11(Z)-pentacosadiene along with a parallel decrease in 7,11-nonacosadiene, significantly reduces copulation in Drosophila . This raises the possibility that 7(Z),11(Z)-pentacosadiene may act as an anti-aphrodisiac.