Plants both anticipate daytime raids by hungry insects and make sophisticated preparations to fend them off, using circadian-rhythm-regulated genes.

Scientists have long known that plants have an internal clock that allows them to measure time regardless of light conditions. In recent years, biologists have begun to apply genetic tools to the study of plant circadian rhythms.

They used 12-hour light cycles to train the circadian clocks of both Arabidopsis plants and a caterpillar that eats Arabidopsis. Plants whose clocks were in phase with the insects were relatively resistant, while plants whose clocks were out of phase were decimated by the insects feeding on them.