The leaves of Pinguicula are yellowish in color, which is probably the source of the common name butterwort. The trapping mechanism of Pinguicula is a simple one. Insects become stuck in the sticky mucilage (which they may mistake for water or nectar). When an insect becomes stuck on the mucilage, the edge of the leaf slowly rolls over. The leaves never completely close. When the insect is digested, the leaf edges unrill and the leaf becomes more nearly flat.