The neuroethology of labeled lines in insect olfactory systems

All insects, including pest insects and vectors of human and animal diseases, use their olfactory system to locate host resources and avoid dangers in their environment. Typically, odor information is coded in a combinatorial fashion in the primary olfactory centers. Insects, however, also possess several olfactory circuits that are narrowly tuned and highly conserved, which allows the dissection of their relevance in guiding complex behaviors, such as courtship, feeding and oviposition. Each specific neural circuit offers an opportunity for highly defined control and manipulation of the associated behavior. Today, we can define the chemosensory systems of model organisms such as Drosophila, linking the tools of chemical ecology with those of neurogenetics and neurobiology. This cross-disciplinary approach has isolated specific olfactory neural circuits that are indeed critical for insect behavior. In this chapter, we identify and define these olfactory-labeled lines, as well as provide examples from the literature.