Abstract
Anagrus atomus (L.) is an egg parasitoid involved in the biological control of Empoasca vitis (Göthe) in vineyards. Sex pheromones play a crucial role in mate finding for several parasitoid species and could be used for monitoring under field conditions. We carried out laboratory and field studies aimed at assessing the existence and identity of a possible A. atomus sex pheromone. We found that males were significantly attracted by virgin females independent of age. Males were not attracted to individuals of the same sex, but they were attracted by a crude extract from an unmated female and its polar fraction. Eugenol (4-allyl-2-methoxyphenol) was identified as the attractive substance and proved to be attractive not only in the olfactometer but also in another laboratory bioassay and under field conditions. Attraction of males, but not females, confirms that this is not an aggregation pheromone. This is the first sex-pheromone component identified in Mymaridae, however more compounds could be involved in the mating behaviour of A. atomus. The utility of a sex pheromone in A. atomus is discussed in the context of fitness returns.
Highlights
Mate finding is a crucial step in the mating system of insects and the use of reliable information may increase both the probability of finding a mate and mating success
Female age did not seem to affect male response. In both Experiments 1 and 2, males exposed to the odour released by a virgin female showed wing fanning and increased locomotory activity. Most males fan their wings in the presence of a virgin female, whereas only a small proportion of those exposed to the odour of a mated female did so
The attraction of A. atomus male wasps to both live virgin females and their crude extracts supports the hypothesis that a volatile sex pheromone is released by females, similar to what has previously been found in other hymenopteran parasitoids (De Lury et al 1999; Eller et al 1984; Nazzi et al 1995; Ruther et al 2000; Salerno et al 2012; Simser and Coppel 1980)
Summary
Mate finding is a crucial step in the mating system of insects and the use of reliable information may increase both the probability of finding a mate and mating success. Several stimuli (e.g. visual and tactile) can be used for this purpose but chemicals produced by members of both sexes are mainly involved (Symonds et al 2009). The range of activity of pheromones can vary. Volatile compounds released by females are used by males for longrange orientation during mate finding (> 2 cm), whereas chemicals of relative low volatility mediate male courtship behaviour at close range (Steiner et al 2006). Sex pheromones play a crucial role in mate finding in most hymenopteran parasitoids (Kainoh 1999; Ruther 2013). The sexpheromone components of more than 20 hymenopteran
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