PERIPHERAL ODOR PERCEPTION BY ADULT APHID FORMS WITH THE SAME GENOTYPE BUT DIFFERENT HOST-PLANT PREFERENCES

As adults, the summer (alate virginopara) and autumn (gynopara) winged forms of the black bean aphid, Aphis fabae, utilise different host plants, the bean Vicia faba, and the spindle tree, Euonymus europaeus, respectively. Electroantennograms (EAGs) were recorded from the antennae of these aphid forms, reared from a single clone, to thirty five plant volatiles and to paraffin oil extracts from leaves of the two host plants. The EAG peak responses were normalised against the adjacent responses to a standard stimulus ((E)-2-hexenal at log 2 dilution). The comparison of different parameters of the EAG responses, i.e. peak, rise and decay, reveals that peripheral olfactory perception of most volatiles is not significantly different between these two forms. In addition, the responses of adult wingless virginoparae to thirteen of the plant volatiles show, with one exception, similar peripheral perception. The results indicate that any odour discrimination between the two alternative host plants by their respective colonisers is not perceived at the level of the peripheral olfactory receptors. The EAG response profile of A. fabae differs from that of the vetch aphid, Megoura viciae, which also colonises bean.