Abstract
This paper reports the results of a comparative laboratory analysis of the behavioural responses of the egg parasitoid Tris- solcus basalis (Wollaston) (Hymenoptera: Scelionidae) to semiochemical cues from four species of pentatomid bugs, Nezara viridula (L.), Eurydema ventrale Klt., Murgantia histrionica Hahn. and Graphosoma semipunctatum F. (Heteroptera: Pentatomidae). In a Y-tube olfactometer, T. basalis was attracted by volatile chemicals from N. viridula, but not from other pentatomid species. In an open arena, the parasitoid reacted to chemical trails left on filter paper by all the species but most intensely to those left by N. viridula. However, upon encountering pentatomid eggs, T. basalis examined more intensely and probed more frequently the eggs of G. semipunctatum than those of the other species. The parasitoid only parasitized and emerged from eggs of G. semipunctatum and N. viridula; those of the other species were unsuitable. Therefore N. viridula is semiochemically confirmed to be a coevolved host (old association) of T. basalis, whereas G. semipunctatum may be a potential non-coevolved host (new association). The utility of these tests for defining a parasitoids' host specificity and in assessing the risk of non-target effects in biological control is discussed.
Highlights
Insect parasitoids are important indicators of species richness and are often used as models for studies on behavioural and chemical ecology
This paper reports the results of a comparative laboratory analysis of the behavioural responses of the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) to semiochemical cues from four species of pentatomid bugs, Nezara viridula (L.), Eurydema ventrale Klt., Murgantia histrionica Hahn. and Graphosoma semipunctatum F. (Heteroptera: Pentatomidae)
The egg parasitoid T. basalis responded in the olfactometer, open arena and confined arena, to cues of its coevolved host N. viridula, and cues of some other bug species
Summary
Insect parasitoids are important indicators of species richness and are often used as models for studies on behavioural and chemical ecology. Female parasitoid foraging behaviour has been divided into a series of hierarchical steps: habitat preference, host community location, host location, host recognition and acceptance, and among the different ecological and physiological factors involved, chemical cues influence all of these steps (Vet & Dicke, 1992; Vinson, 1998; Steidle & van Loon, 2002). Recent research has shown the importance of host semiochemicals in determining host specificity in parasitoids (Meiners et al, 2000; Conti et al, 2004). Such studies suggest new ways of evaluating and predicting the possible adverse side effects of biological control agents on non-target species (Conti et al, 2004). Studies of the chemical cues involved in host/prey selection behaviour (Vet & Dicke, 1992; Vinson, 1998) provide a quantifiable characterization of host specificity
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