Insect communities consist of several trophic levels that have to forage for suitable resources among and within larger patches of non-resources. To locate their resources, insects use diverse stimuli, including olfactory, visual, acoustic, tactile and gustatory cues. While most research has focused on cues derived from plants and other insects, there is mounting evidence that insects also respond to volatile organic compounds (VOCs) emitted by microorganisms. However, to date only very little is known about the olfactory responses of insects to microbial VOCs within and across different trophic levels. In this study, using Y-tube bioassays and chemical analysis of VOCs we assessed how volatile compounds emitted by bacteria affect the olfactory response of insects of different trophic levels. Experiments were performed using two aphid species (Amphorophora idaei and Myzus persicae var. nicotianae), their most important primary parasitoid species (Aphidius colemani, A. ervi, and A. matricariae), and two of their hyperparasitoid species (Asaphes suspensus and Dendrocerus aphidum). Olfactory responses were evaluated for three bacterial strains (Bacillus pumilus ST18.16/133, Curtobacterium sp. ST18.16/085, and Staphylococcus saprophyticus ST18.16/160) isolated from the habitat of the insects. Results revealed that insects from all trophic levels responded to bacterial volatiles, but responses varied between and within trophic levels. All bacteria produced the same set of volatile compounds but often in different relative concentrations. For a number of these volatiles we found contrasting correlations between their concentration and the behaviour of the primary parasitoids and hyperparasitoids. Exploitation of such contrasting responses may lead to novel semiochemical-based strategies to improve biological aphid control.

The spotted wing drosophila, Drosophila suzukii, is an invasive pest species from Southeast Asia that was recently introduced in Europe and North America. As this fruit fly lays its eggs in ripening soft-skinned fruit, it causes great damage to a variety of crops, including cherries, blueberries, blackberries, raspberries, grapes, plums and strawberries. Consequently, there is a great demand for an effective and species-specific lure, which requires the development of successful attractants. Until now, there is no lure available that is species-specific and can detect the presence of D. suzukii before infestation. As blackberry (Rubus fruticosus) is one of the preferred host crops of D. suzukii, the volatile compounds of R. fruticosus berries are here identified and quantified using multiple headspace SPME (solid phase micro extraction) GC-MS (gas chromatography–mass spectrometry). Subsequently, the attractivity of 33 of the identified compounds was tested with a two-choice laboratory bioassay. Acetaldehyde, hexyl acetate, linalool, myrtenol, L-limonene and camphene came out as significantly attractive to D. suzukii. The first four attractive compounds induced the strongest effect and therefore provided the best prospects to be implemented in a potential lure. These findings could contribute towards the development of more effective attractants for monitoring and mass trapping D. suzukii.

Enmeshed in various social structures, humans must often weigh their own interest against the interest of others—including the common interest of groups they belong to. The Public Goods Game (PGG), which succinctly pits individual interest against group interest, has been a staple of research into how people make such decisions. It has been studied in many variations, in the laboratory and (increasingly) online. One of the defining parameters of the PGG is the marginal per capita return of the group project (MPCR), which determines the incentive for contributing to the group project relative to the incentive of keeping points in the personal account. The effect of MPCR on contributions has been investigated before, but its effects have never been characterised with high resolution. Here, we present a systematic and high-resolution investigation of the effect of MPCR in groups of three. We do this in a large-scale online decision making experiment recruiting participants from Amazon Mechanical Turk. Our results provide a fine-grained account of the relationship between incentive to cooperate on the one hand and cooperation on the other, and can help to provide a basis for choosing MPCR magnitudes for future research endeavours using online PGG studies.

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Insect communities consist of several trophic levels that have to forage for suitable resources among and within larger patches of non-resources. To locate their resources, insects use diverse stimuli, including olfactory, visual, acoustic, tactile and gustatory cues. While most research has focused on cues derived from plants and other insects, there is mounting evidence that insects also respond to volatile organic compounds (VOCs) emitted by microorganisms. However, to date only very little is known about the olfactory responses of insects to microbial VOCs within and across different trophic levels. In this study, using Y-tube bioassays and chemical analysis of VOCs we assessed how volatile compounds emitted by bacteria affect the olfactory response of insects of different trophic levels. Experiments were performed using two aphid species (Amphorophora idaei and Myzus persicae var. nicotianae), their most important primary parasitoid species (Aphidius colemani, A. ervi, and A. matricariae), and two of their hyperparasitoid species (Asaphes suspensus and Dendrocerus aphidum). Olfactory responses were evaluated for three bacterial strains (Bacillus pumilus ST18.16/133, Curtobacterium sp. ST18.16/085, and Staphylococcus saprophyticus ST18.16/160) isolated from the habitat of the insects. Results revealed that insects from all trophic levels responded to bacterial volatiles, but responses varied between and within trophic levels. All bacteria produced the same set of volatile compounds but often in different relative concentrations. For a number of these volatiles we found contrasting correlations between their concentration and the behaviour of the primary parasitoids and hyperparasitoids. Exploitation of such contrasting responses may lead to novel semiochemical-based strategies to improve biological aphid control.