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Odorant-binding proteins were studied in the noctuid moths Agrotis segetum, Autographa gamma, Helicoverpa armigera, Heliothis virescens and Spodoptera littoralis using antisera raised against the pheromone-binding protein (PBP) and general odorant-binding protein 2 (GOBP2) of Antheraea polyphemus (Saturniidae). Proteins immunoreacting with these antisera were only found on the antennae and PBP and GOBP2 could be identified on western blots of males and females of all five species. PBPs were predominantly localized in sensilla trichodea and GOBP2 in sensilla basiconica, in good correlation with the stimulus specificity of the receptor cells in these sensilla. In H. armigera and H. virescens the majority of the s. trichodea immunoreacted with the antiserum against PBP of A. polyphemus; in A. segetum, A. gamma and S. littoralis, on the other hand, a high percentage of s. trichodea remained unlabelled. Probably, the PBP expressed in these sensilla is so different that it does not immunoreact with the antiserum used. Such a protein was found by native PAGE of antennal extracts of A. segetum and S. littoralis. These data correlate with the fact that the two heliothine species use pheromones with the same alkyl chain length as A. polyphemus, while the other three species use pheromones with shorter chains. In H. armigera, H. virescens, A. gamma and S. littoralis female antennae were also immunolabelled and a large number of PBP-expressing s. trichodea was consistently found. In S.littoralis this fits with the electrophysiologically recorded high pheromone sensitivity of female s. trichodea, whereas in females of H. armigera and H. virescens no or only weak responses to pheromone stimulation have been reported. Therefore, PBP expression in a sensillum does not necessarily imply pheromone sensitivity of its receptor cells.

The antennal sensilla of Myzus persicae were mapped using scanning and transmission electron microscopy. Placoid sensilla and coeloconic sensilla were found on the 6th segments, whereas 2 types of trichoid sensilla were present all through the length of the antenna. A single sensillum placoideum was located on the 5th segment, whereas alate aphids also presented placoid sensilla on the 3rd antennal segment. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of antennal chemosensilla. The antiserum against OBP7 intensively labeled all placoid sensilla from both primary and secondary rhinaria, with gold granules concentrated in the lymph surrounding the dendrite. OBP6 and OBP3 could also be detected in placoid sensilla, but less strongly than OBP7. Barely significant reaction or no reaction was observed with antibodies against OBP8.

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