Some think all trap types have a similar basic structure—the hairy leaf. Hairy leaves do catch and hold drops of rainwater, which helps bacterial growth. Insects land on the leaf, are caught by the surface tension of the water, and suffocate. Bacteria start to decay the insect, and release nutrients from the corpse. The plant then absorbs the nutrients through its leaves. This 'leaf feeding' can be found in many non-carnivorous plants. Plants that were better at holding water and insects therefore had a selective advantage. Rainwater can be retained by cupping the leaf, leading to pitfall traps. Alternatively, insects can be caught by making the leaf stickier, leading to flypaper traps.