Insectivorous plants passively eat insects. Their adaptations trap insects that happen to land on them. It takes no thought on the part of the plant. But why do these plants need to eat insects? They are green plants that can photosynthesize their own foods. The answer to this is simple. Insectivorous plants grow in mineral poor soil or very wet areas where all the nutrients are washed from the soil regularly. Without these minerals that the plants can pull from the soil, they struggle to survive. So insectivorous plants supplement their meager food making skills by trapping insects and dissolving them to absorb their essential minerals -- like nitrogen.