Olfactory attraction mediated by the maxillary palps in the striped fruit fly, Bactrocera scutellata: Electrophysiological and behavioral study

Abstract

Here, we report that the olfactory attraction of the striped fruit fly, Bactrocera scutellata (Hendel; Diptera: Tephritidae), a serious pest of pumpkin and other cucurbitaceae plants, to cue lure and raspberry ketone is mediated by the maxillary palps. The antennae, bearing three morphological types (basiconic, trichoid, and coeloconic) of olfactory sensilla, in male and female B. scutellata exhibited significant electroantennogram (EAG) responses to a plant volatile compound, 3-octanone, and methyl eugenol, whereas cue lure, raspberry ketone, and zingerone that are known to attract several other species of Bactrocera fruit flies elicited no significant EAG responses from both sexes. In contrast, maxillary palps, housing one morphological type of basiconic sensilla, displayed the largest electropalpogram (EPG) responses to cue lure followed by raspberry ketone among the five compounds tested in male and female B. scutellata, with only minor EPG responses to 3-octanone, which indicates that the maxillary palps are responsible for detecting cue lure and raspberry ketone in this species. In field trapping experiments, significant number of male B. scutellata were captured in the traps baited with cue lure or raspberry ketone, in which the attractiveness of cue lure was significantly higher than that of raspberry ketone. Methyl eugenol and zingerone were not behaviorally attractive to B. scutellata although they elicited significant EPG responses. Our study indicates that the behavioral attraction of B. scutellata to cue lure and raspberry ketone is mediated by the olfactory sensory neurons present in the maxillary palps.