Repeatability of Pheromone Blend Composition in Individual Males of the Southern Green Stink Bug, Nezara viridula

The males of Nezara viridula (Heteroptera, Pentatomidae) produce a blend of four terpenoid compounds. The proportion of these four compounds varies among different populations. The terpenoid content of the volatile emission from individual males of a French population was monitored for several days with headspace solid-phase microextraction. The total amount of terpenoid compounds collected on an SPME fiber from one virgin male bug emitting over the course of 1 hr was very variable between samples. More than 50% of males released pheromone, at least during one part of the observation period. The relative percentages of bisabolene, nerolidol, trans-bisabolene epoxide, and cis-bisabolene epoxide were calculated and compared. The proportion of nerolidol in the blend showed a large dispersion between samples and a high coefficient of variation. The percentage values for bisabolene and its trans and cis epoxides were less dispersed, and the coefficients of variation for both epoxides were low. The proportion of trans epoxide relative to the two epoxides, which has been considered characteristic of pheromone strains of N. viridula, showed the smallest coefficient of variation. The repeatability index (RI) varied between 0.57 and 0.85 for the four compounds. Repeatability was particularly high for the two epoxide isomers. Stability in epoxide production was confirmed by statistical analysis (ANOVA), which revealed significant differences in the percentages of cis and trans epoxides between individuals. Correspondingly, the RI of the ratio of trans to cis + trans epoxides was over 0.8. Our study confirms the existence of an interindividual variation of the trans to cis epoxide ratio within populations of Nezara viridula but indicates that each individual reproducibly emits both isomers in the same proportion day after day.