Moths seek out favorite flowers.

• Position: Insects

Although a plant's odor can be composed of hundreds of chemicals, a moth uses just a handful to recognize a flower, according to researchers at the University of Arizona, Tucson. It is like identifying a piece of music from hearing only the notes played by a few key instruments, indicates Jeffrey A. Riffell, research fellow in the Division of Neurobiology. "The moth isn't paying attention to all the chemicals at the same time. It's actually just paying attention to a few."

The finding provides insight into how the brain processes a specific smell from the sea of odors floating through the air. Scientists recorded from the brains of tobacco hornworm moths as they smelled each individual chemical of the 60-some that comprise the fragrance emitted by the moth's preferred source of nectar, sacred datura flowers.

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This is the first time researchers have recorded an insect's brain activity as it smelled all of the individual chemicals captured from a real flower. Previous research used only synthetic odors. Just nine of the chemicals provoked a neural response. However, all nine had to be presented simultaneously for the moth to fly to the odor's source and then stick out its tongue seeking nectar.

How the brain-olfactory system decodas odor stimuli is not well understood. "Two-thirds of the male moth's brain is geared toward the environment," Riffell reports. "For female moths, it's about 90%."

Tobacco hornworm moths, known to scientists as Manduca sexta...