Breaking a paradigm: male-produced aggregation pheromone for the Colorado potato beetle

A male-produced aggregation pheromone was identified for the Colorado potato beetle Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae). While male beetles produced only minor amounts of the pheromone, its production could be enhanced by topical application of juvenile hormone III (JH III) (eightfold), by antennectomy (40-fold) or by the combined treatment of JH III and antennectomy (almost 200-fold); this enhancement enabled the identification of the compound as (S)-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol [(S)-CPB I], a unique structure for an insect pheromone. Antennal receptors of both sexes responded selectively to the (S)-enantiomer. Both male and female Colorado potato beetles were attracted to serial source loads of (S)-CPB I in laboratory bioassays; (R)-CPB I was inactive or inhibitory, as demonstrated by the inactivity of the racemate. This is the first identification of a pheromone for the Colorado potato beetle and differs from the paradigm of a female-produced pheromone for this insect. The attractant is also the first male-produced pheromone identified for the Chrysomelidae. The discovery that both JH III and antennectomy increase levels of the pheromone (S)-CPB I indicates the existence of a feedback system involving antennal input, and this system may be under hormonal control.