Electrophysiological and behavioural responses of the housefly to sweet volatiles of the flowers of Caralluma europaea (Guss.) NE Br.

In sapromyiophilous plants, up to date, long range attraction of fly pollinators has been thoroughly investigated and attributed to fetid floral compounds, while the sweet floral scent fraction has not been specifically investigated and its role has received little attention. The aim of the present study was to verify if terpenoids, which are the main compounds of the floral bouquet of Caralluma europaea, play a role in the attraction of its pollinator Musca domestica. Terpinolene, alpha-terpinene and linalool, described as the three main volatiles of the flowers of C. europaea, were evaluated in electrophysiological investigations and blends of these compounds as well as the whole fresh flowers were used in behavioural assays. Antennae of housefly adults showed positive dose-dependent responses to all the chemicals tested. Houseflies were attracted by the odour of the fresh flowers and by the reconstructed terpenoid blend at the dose of 100 mu g. At the dose of 10 mu g, the blend did not produce any attraction. The results of the present study support the hypothesis that terpinolene, alpha-terpinene and linalool emitted by C. europaea flowers are involved in pollinator attraction and demonstrate the importance of the sweet scent in this sapromyiophilous species.