1INRA, Unité de Phytopharmacie et Médiateurs Chimiques, Route de Saint Cyr, 78026 Versailles Cedex, France.
2NIB, Laboratory for Neurobiology Laboratory, Vecna Pot 111, P.O.B. 141, 1001 Ljubljana, Slovenia.
Premating behavior in the southern green stink bug, Nezara viridula, involves vibratory and chemical communication. Males produce a volatile pheromone which attracts females from a distance. The song repertoire of male and female Nezara is composed of a variety of substrate-transmitted signals. The pheromone components have been identified and the frequency and temporal structure of the different vibratory signals have been analyzed. However, the specific order in which the two sensory modalities act has not been described. Thus, a conjunction of techniques including olfactory stimulation, volatile collection, song recording and playback of acoustic signals, was used to determine the precise temporal and spatial pattern of interactions between olfactory and vibratory communication. Males start to produce pheromone at age 8-10 days. We did not observe any conspicuous calling behavior and pheromone production does not follow a circadian rhythm. Stimulation of males with female calling song (FCS) failed to trigger the pheromone production and isolated males emit as well. Virgin females rarely emit the FCS spontaneously, but they respond with FCS emission to the presentation of male volatiles or of synthetic pheromone. When put on a new plant, males spontaneously emit male courtship song (MCrS) and when a couple was observed on a loudspeaker, it was usually the male who started singing first. On a plant, males alternate with the pre-precorded FCS by emitting MCrS and they increase their locomotion. Males are able to locate the source of female song. According to the present state of knowledge, signals of both modalities interact to improve mate finding and recognition.