Plants release volatile chemicals when attacked by caterpillars.
For a moth, identifying a plant that already has caterpillars on it has several advantages. The moth can avoid competition for her offspring and steer clear of plants that will already have mobilized their chemical defences to make themselves less palatable. It could also be a way to avoid predatory insects that also detect the volatile chemicals and home in on the caterpillars. The findings could lead to the development of 'natural' pesticides that are less detrimental to the environment. Caterpillar-induced nocturnal plant volatiles repel conspecific females.