Susanna M. ANDERSSON*, Gunnar BERGSTRÖM
Department of Chemical Ecology, Botanical Institute, Göteborg University, Carl Skottsbergs
Gata 22, S - 413 19 Gothenburg, SWEDEN
Aglais urticae (Nymphalidae, Lepidoptera) is one of the few Scandinavian butterfly species that hibernates as an adult. In the autumn males and females have the same nutritional requirements, and feed nectar ffom flowers in order to build up a supply of lipids to be used during hibernation In this paper we investigate the importance of floral scent for the attraction to flowers by nectar searching A.urticae.
Individuals from a wild population were given a choice between scented and non- scented flower dummies. The flower dummies were made of plastic film cans with four layers of mauve coloured cheesecloth covering the top of the can (Dobson, Heidi). The size and colour of the dummies were chooser to mimic the real flowers that were used as scent sources. In scented dummies cut flowers in bloom releasing scent were stuck up in the film cans while flower buds not releasing any scent were used for the not scented dummies. The butterflies could not see or reach the flowers through the cheescloth. No reward was given in the dummies during bioassay.
Five different plant species normally visited by A.urticae was used as scent sources in flower dummies, the wild growing Centaurea scabiosa, Cirsium arvense (Compositae), Knautia arvensis (Dipsacaceae), and Oregano vulgare (Lamiaceae), and the cultivated Buddleia davidii (Loganiaceae) is cultivated.
In comparison to not-scented dummies, the scented dummies more often attracted butterfly individuals at a distance of at least 70 centimeters. This was the case with both naive individuals and individuals that earlier had been foraging from flowers that were used as scent source. Furthermore, the scented dummies elicited nectar search for longer time than not scented ones. Individuals experienced to foraging on C.arvense visited more often dummies with this scent and stayed for a longer time in comparison to dummies with a not earlier encountered scent from B.davidii. Butterflies were able to discen scent previously connected to rewarding flowers from a unknown or new scent.