Odour-mediated nectar foraging in the silver Y moth, Autographa gamma (Lepidoptera : Noctuidae): behavioural and electrophysiological responses to floral volatiles

Naive male and female silver Y moths, Autographa gamma (Lepidoptera: Noctuidae), were attracted in a flight tunnel assay to potted creeping thistle, Cirsium arvense (Asteraceae), butterfly-orchid, Platanthera bifolia (Orchidaceae), soapwort, Saponaria officinalis (Caryophyllaceae), greater knapweed, Centaurea scabiosa (Asteraceae), red clover, Trifolium pratense (Fabaceae), and catnip, Nepeta faasseni (Labiatae), plants with flowers. The most attractive plants were C. arvense, P. bifolia and S. officinalis that elicited 87, 78 and 65%, source contacts, respectively. C. scabiosa was less attractive eliciting 43%, response. T. pratense and N. faasseni showed the least attraction eliciting 28 and 26% source contacts, respectively. A cotton plant used as control, was not attractive. Floral volatiles from the investigated plant species were collected using headspace sampling technique. Samples were analysed using gas chromatography coupled with electroantennographic detection, and electrophysiologically active compounds were identified by coupled gas chromatography/mass spectrometry. Consistent electrophysiological responses were elicited by twelve compounds from headspace of C. arvense, thirteen compounds from P. bifolia, eleven compounds from S. officinalis, nine from C. seabiosa, ten from T. pratense and two from N. faasseni. Most of the active compounds were specific for one or two species, while benzyl benzoate was present in four and benzaldehyde and benzyl alcohol in three species. Floral scents of C. arvense, P. bifolia and S. officinalis, the most attractive flowers, were dominated by aromatic compounds that were not abundant in the scent of other flowers. To conclude, the results demonstrate the absence of a common denominator of odours present in flowers of different plants visited by A. gamma