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Chemical ecologists are identifying the visual and chemical cues that allow insects to find food.

Decoding an Insect's Sensory World W hen Shannon B. Olsson first moved to Bangalore, India, to start her lab at the National Centre for Biological Sciences at the Tata Institute of Fundamental Research in 2014, she was struck by all the curious foods in the city's markets. "There are all these unfamiliar gourdsbitter gourds, elephant gourdsthat I didn't know what to do with," she says.Having lived and worked on three continents, Olsson had certainly sussed out sources of food in novel environments before. But it got her thinking about the insects she studieshoverflies. This family of insects lives in a wide range of different habitats, including tropical, alpine, and subarctic regions. How do they know which flowers are food, when flowers look and smell so different in areas like India and Sweden and the U.S.? Karin L. Nordström, a neuroscientist at Flinders University who studies how insects visually perceive their world while movingseeing on the fly, as it werehad a related question. Nordström uses wild hoverflies for her experiments, and while catching them she noticed that they would all go to the same flowersones that to her looked identical to the ones right next to them, which the hoverflies routinely ignored.Hoverflies are one of the most prominent pollinators on the planet behind bees, but unlike bees they are solitary; once the larvae hatch, they are on their own, with no one to teach them what food sources to prefer. Whether it's an individual fly choosing from an array of flowers or a worldwide preference by the flies for specific cues, Olsson and Nordström hypothesized that these insects must have an innate template that helps them find flowers wherever they are. They set out to identify what exactly draws these insects to their food.Such work asks theoretically fascinating questions about insect perception, but it also has a practical dimension. The decline in bee populations and the threat it poses to farming has been big news in the U.S. and Europe, and many of the