Question

if a pitcher plant is green and carries out photosynthesis why does it feed on insects?

Answer 1

The pitcher plants are not exactly green in colour and they lack chlorophyll which helps in the making of food for the plants.
The pitcher plants are carnivores and feed on insects.

Answer 2

Pitcher plants are carnivorous and it need fragrance material from the insect to attract other insects which is taken from other plants to continue the cycle.
It's not correct by it's from my point of view