Abstract Bactrocera umbrosa (Fabricius) is an oligophagous fruit fly of economic importance that infests mainly Artocarpus fruits (Moraceae). The sexual communication system of this species is poorly understood, partly due to difficulties in establishing laboratory colonies. Males of B. umbrosa are strongly attracted to and voraciously fed on methyl eugenol (ME), a naturally occurring plant secondary compound. Here, we elucidate the endogenously produced and ME–derived chemical signals involved in the species’ communication. Gas chromatography–mass spectrometry analyses of pheromonal glands revealed that immature males produced four endogenous compounds, whereas sexually mature males produced six additional volatile compounds, including the terpenoids ( R )-6-methyl-2-vinylhept-5-ene-1,2-diol and ( S )-7-methyl-3-methyleneoct-6-ene-1,2-diol, which, to our knowledge, have not previously been documented in insects. Following ME ingestion, males accumulated six ME metabolites—eugenol, isoeugenol, ( S )-1ʹ-hydroxymethyleugenol (( S )-1ʹ-HME), 2-allyl-4,5-dimethoxyphenol (DMP), ( Z )-3,4-dimethoxycinnamyl alcohol (Z-DMC), and ( E )-coniferyl alcohol (E-CF). Behavioral assays using a Y-tube olfactometer demonstrated that two endogenous compounds (3-ethyl-2,5-dimethylpyrazine and 6-oxo-1-nonanol) and two ME metabolites (DMP and E-CF) significantly attracted virgin females during courtship. In contrast, none of the endogenous volatiles was attractive to the males, whereas three ME metabolites—eugenol, isoeugenol, and DMP—elicited significant male attraction during dusk. These findings demonstrated that B. umbrosa utilizes endogenous compounds as sex-specific signals to attract conspecific females, while distinct ME-derived metabolites mediate both male-male and male-female communication, facilitating male aggregation and enhancing sexual attraction. These insights contribute to a deeper understanding of the intricate glandular chemistry and chemical communication system of the Artocarpus fruit fly, which may inform future strategies for its control and management.
Kiuchi et al. (Mon,) studied this question.