Effects of methyl eugenol and raspberry ketone/cue lure on the sexual behavior of Bactrocera species (Diptera: Tephritidae)

Bactrocera is a speciose genus of tephritid fruit fly that includes several important pests of fruits and vegetables. Detection and control of these pestiferous species rely heavily upon male attractants or lures, with different Bactrocera species responding to either methyl eugenol (ME) or raspberry ketone (RK.; or its man-made analogue cue lure, CL). Despite their usage worldwide, the function of ME and RK/CL in the natural history of Bactrocera flies is poorly known. The purpose of this review is to summarize research on the potential role of ME and RK/CL as pheromone precursors or components-in the sexual communication of Bactrocera species. The topics covered include i) male feeding behavior on ME or RK/CL, ii) the fate of ingested lures, iii) female and male attraction to lure-fed males, and iv) mating success of lure-fed males. Data are available for only a few species, but they provide solid evidence for a role of male lures in mating behavior. For several ME-responding species, research has shown that i) ME metabolites are incorporated and emitted along with endogenously produced components of the male sex pheromone, ii) females show preferential attraction to pheromone containing these metabolites, and iii) males fed ME (or plants containing ME) enjoy increased mating success over non-fed males. Fewer studies have been conducted on RK/CL-responding species, and these reveal i) the lure is not broken down or metabolized but is sequestered (and presumably emitted) as RK, ii) females show preferential attraction to pheromone produced by males that fed upon RK/CL, and iii) RK/CL ingestion produces a significant, but short-lived (1 d), boost in male mating success. Potentially productive avenues of future research are discussed.