Why do carnivorous Caryophyllales plants digest insects and other small animals?

Carnivorous plants within the Caryophyllales order—such as those in the families Droseraceae and Nepenthaceae—do not consume insects and other small animals as a primary source of energy. Like most other plants, they are photosynthetic and manufacture their own sugars using sunlight, water, and carbon dioxide.12

Instead, these plants have evolved to capture and digest prey to obtain nitrogen and other essential nutrients that are often scarce or unavailable in the poor, acidic, or otherwise hostile soils where they typically grow. By utilizing specialized trapping mechanisms—such as snap traps, sticky flypaper leaves, or pitfall pitchers—these plants can thrive in ecological niches like bogs and wetlands that would be challenging for many other species to inhabit. Through the use of enzymes or bacteria, they break down their prey to absorb these vital compounds, effectively augmenting their diet to survive in nutrient-depleted environments.213