Car exhaust and other urban fumes can disrupt moths’ ability to make their way to flowers, a new study reports.

“The flowers occur in patches that can be kilometers away, and these moths are almost at the edge of survival trying to find them,” said Jeff Riffell, a biologist at the University of Washington and the first author of the study, which appears in the journal Science.

The research focuses on the tobacco hornworm moth, which depends on nectar for energy. Nectar from one flower provides enough fuel for just 15 minutes of flying time, so “flying around is really energetically expensive,” Dr. Riffell said.

The scientists sampled flower scents and other odors with a sensitive mass spectrometer, and then used a wind tunnel to determine how different combinations of smells affected a moth’s ability to find flowers. They found that the moths did far better in rural environments than in urban and suburban ones.