Why do some plants feed on …

1)Some Plants feed on insects because they grows in a type of soil which is unable to supply Nitrogen(N).so they feed on insects.

2)Most of the pitcher plants have se type of Most of the pitcher plants have some type of lure to attract insects. Many of them have attractively colored, elongated pitchers with nectar. Some species produce scents to attract their prey. The prey that enters the pitcher cannot escape, as the structure has slippery inner surfaces. The trapped prey will eventually drown in the liquid inside the pitcher. The liquid has digestive enzymes (secreted by the plant) that will dissolve the prey gradually.

In some species, the liquid in the pitcher contains bacteria that act on the prey to decompose the latter. Some others have insect larvae, that feed on the trapped insects, and the plant absorbs the excreta of the larvae. These plants share a symbiotic relation with such larvae. Once the prey gets decomposed, the plant extracts amino acids, peptides, phosphates, ammonium, and urea from the solution.