• melanoleuca
    +3

    Great question! Carnivorous plants, like pitcher plants and Venus fly traps, generally grow in low nutrient soil and need additional nitrogen that they can't get through their roots. Thus, they have evolved the ability to trap and digest insects. Why not bigger organisms like bats? Well, digestion is VERY expensive in terms of energy. Pitcher plants have already sacrificed their energy producing ability by modifying their leaves into cone shapes. This means that the leaves don't intercept as much sunlight which, in turn, means they don't photosynthesize as much and have less energy available to do plant stuff. So, trapping insects or bat guano is a happy medium between obtaining nitrogen and spending excess energy on digestion.