How are cabbage white butterflies related to plants in the mustard family?

Cabbage white butterflies (genus Pieris) are closely related to plants in the mustard family (Brassicaceae) through a specialized herbivore-host relationship.

While most plants in the Brassicales order produce sulfur-containing compounds called glucosinolates—or mustard oils—to deter predators, these same chemicals act as an attractant for cabbage white butterflies. Consequently, the larvae of these butterflies feed on cabbage and other related crops within the mustard family.123

Because of this feeding behavior, cabbage whites are considered significant economic pests, capable of decimating cultivated Brassica crops. While some related plants in the order, such as Resedaceae, remain largely pest-free, the mustard family is frequently targeted by these butterflies.21