18 - Polyene hydrocarbons, epoxides, and related compounds as components of lepidopteran pheromone blends

Summary

Moth species rely heavily to exclusively on sex attractant pheromones for long-range location of mates. In most but not all species, the attractant pheromone is produced by females, and males have evolved extremely sensitive antennae, the receptors of which are tuned specifically to detect the scent of conspecific females. It is clearly a very effective mate location system, because male moths have been shown to be attracted to females over distances of a kilometer or more (Mell, 1922; Collins and Potts, 1932), despite the fact that females may only produce micrograms to nanograms of pheromone per hour. To be effective as long-range, species-specific attractants, sex attractant pheromones should fit several criteria. First, they must have sufficient vapor pressure under ambient temperature conditions to provide a detectable signal for males to find and follow. Thus, attractant pheromones are relatively small molecules, with most having molecular weights of less than 300 Daltons. They also tend to have few or even no polar functional groups, because polar functional groups decrease volatility. Second, the individual components of the pheromone, or the blend of components, must be sufficiently distinctive that they form a unique, species-specific blend, so that there is no cross-attraction among sympatric species (see Chapter 7). Whereas there are cases known in which species appear to produce unique compounds, the majority of insects appear to create species-specific signals by blending two or more compounds, each of which may be shared by several species, in specific ratios.