How useful are olfactometer experiments in chemical ecology research?

Olfactometer experiments, in which arthropods are given the choice between two or more odor sources to test behavioral preferences, are commonly used in chemical ecology research. Results of such often lead to conclusions on behavior in an ecologically relevant setting. However, it is widely unknown how well these experiments reflect actual behavior in nature. Recently, we used natural insect herbivores of wild lima bean plants to evaluate their behavior in Y-tube olfactometer experiments compared with feeding experiments. We demonstrated that depending on volatile concentration, insect sex significantly determined preference, and that independent of sex, the actual feeding choice of insects depended on defensive short-distance cues, which did not correlate with volatile cues emitted by the plants. Thus, our study shows that olfactory decisions do not reflect actual feeding choice and that olfactometer experiments may only provide a limited and simplified picture of actual decision making by insects.