The pink hibiscus mealybug (PHM) is an extremely polyphagous insect that feeds on a wide range of host plants and inflicts severe damage throughout much of the world. This pest appears to be native to Australia or Southern Asia and has been spreading to Southern California, Mexico, Central America and, most recently, to Florida in 2002. Agricultural crops in the United States expected to be at greatest economic risk to PHM invasion include ornamentals, vegetable crops, citrus, grapes, and avocados. Potential losses of $750 million per year have been estimated if the insect cannot be controlled. Two new compounds that together constitute the female sex pheromone of the PHM were isolated, identified, and synthesized. They are (R)-2-isopropenyl-5-methyl-4-hexenyl (S)-2-methylbutanoate [common name is (R)-lavandulyl (S)-2-methylbutanoate)] and [(R)-2,2-dimethyl-3-(1-methylethylidene)cyclobutyl]methyl (S)-2-methylbutanoate (which we refer as (R)-maconelliyl (S)-2-methylbutanoate). Maconelliol is a novel cyclobutanoid monoterpene, and its structure has been established by enantioselective synthesis from precursors of known structure and configuration. A 1 : 5 synthetic mixture of the two RS esters (1 micro-gram/rubber septum) proved to be a potent attractant in field bioassays. The pheromone component, maconelliyl 2-methylbutanoate, represents a heretofore undescribed natural product. This synthetic pheromone will provide a much more economical, convenient, and useful survey tool for PHM population monitoring to facilitate eradication programs, and sex attractant-baited traps will also be useful in the study of seasonal life history of PHM. Furthermore, the pheromone will enable the future development of mass trapping, attract-and-kill, and mating disruption technologies for the growers to manage this pest.