Odor detection in insects: volatile codes.

Insect olfactory systems present models to study interactions between animal genomes and the environment. They have evolved for fast processing of specific odorant blends and for general chemical monitoring. Here, we review molecular and physiological mechanisms in the context of the ecology of chemical signals. Different classes of olfactory receptor neurons (ORNs) detect volatile chemicals with various degrees of specialization. Their sensitivities are determined by an insect-specific family of receptor genes along with other accessory proteins. Whereas moth pheromones are detected by highly specialized neurons, many insects share sensitivities to chemical signals from microbial processes and plant secondary metabolism. We promote a more integrated research approach that links molecular physiology of receptor neurons to the ecology of odorants.