BACKGOUND Sex pheromones of the fall armyworm, Spodoptera frugiperda, show differences in composition and proportions in different geographical populations, but always contain Z9‐14:OAc as the major component. Odorant receptor neurons (ORNs) housed in the long trichoid sensilla (TS) of male antennae are essential to detect female‐released sex pheromones in moths. RESULTS In this study, we identified seven components from pheromone gland extracts of female S. frugiperda in the Yunnan population from China, including (Z)‐7‐dodecen‐1‐yl acetate (Z7‐12:OAc), (Z)‐9‐tetradecenal (Z9‐14:Ald), (Z)‐9‐dodecen‐1‐yl acetate (Z9‐12:OAc), (Z)‐9‐tetradecen‐1‐yl acetate (Z9‐14:OAc), (E)‐11‐tetradecen‐1‐yl acetate (E11‐14:OAc), (Z)‐11‐tetradecen‐1‐yl acetate (Z11‐14:OAc) and (Z)‐11‐hexadecen‐1‐yl acetate (Z11‐16:OAc) at a ratio of 1.2:4:0.8:79.1:1.6:1.6:11.7 by gas chromatography coupled with mass spectrometry. Gas chromatography‐electroantennographic detection showed that Z9‐14:OAc, Z7‐12:OAc and Z11‐16:OAc are the male antennal active components. Peripheral coding of pheromones in males was investigated by single sensillum recording. Five functional neurons housed in three types of TS were identified based on profiles of neuronal responses, which are responsible for attractive component Z9‐14:OAc, synergistic components Z7‐12:OAc, Z11‐16:OAc, interspecific pheromones (Z)‐9‐tetradecen‐1‐ol (Z9‐14:OH) and (Z,E)‐9,12‐tetradecadien‐1‐yl acetate (Z9,E12‐14:OAc), respectively. Wind tunnel and field tests demonstrated that a ternary combination of Z9‐14:OAc, Z7‐12:OAc and Z11‐16:OAc at a ratio of 88:1:11 shows the strongest attractiveness to males. Conclusion An optimized pheromone blend of Z9‐14:OAc, Z7‐12:OAc and Z11‐16:OAc in an 88:1:11 ratio was identified for monitoring the invasive pest S. frugiperda in China. Five functional ORNs encoding intra‐ and interspecific pheromones were identified in male antennae, of which three neurons encode attractive component Z9‐14:OAc, synergistic components Z7‐12:OAc and Z11‐16:OAc, respectively, and the other two neurons encode interspecific pheromones Z9‐14:OH and Z9,E12‐14:OAc, separately. © 2022 Society of Chemical Industry.

Background: Olfaction has an indispensable role in insect behavior, enabling location of suitable host plants and oviposition sites, finding mates and evasion of natural enemies. Chemosensory proteins (CSPs) function to screen external odorants and transport them to olfactory receptor neurons, thereby increasing the sensitivity of the olfactory system. At present, CSP genes have been identified in many insect species, but there are relatively few studies on the function of CSP, especially in Tephritidae.Results: In this study, we sequenced and analyzed 12 transcriptomes of Bactrocera minax and identified five CSP genes. The results of polymerase chain reactions with reverse transcription showed that BminCSP3 was highly expressed only in antennae. Results from competitive binding experiments showed that BminCSP3 has good binding ability to citral compared with 23 other volatile organic compounds. The docking model with citral showed hydrogen bond formation with residues (ARG97); however, no hydrogen bonds were formed in the docking of five other ligands (furfuryl alcohol, linalool, cis-3-hexenyl acetate, (R)-(+)-limonene and (+)-carvone). Electroantennogram (EAG) analyses revealed that citral was active in B. minax at the antennal level, and the EAG response value of female adults was significantly higher than that of male adults. Furthermore, the results of behavioral bioassays showed that females were significantly attracted to citral. Conclusion: Our results suggest that BminCSP3 plays an important role in the recognition of citral by B. minax adults.