Pitcher plants live in boggy areas with a shortage of nitrogen in the soil. To get more nitrogen, pitcher plants capture and consume insects. Pitcher plants have hollow leaves that catch rainwater. Insects that land on the leaf slide down into the pool of water, where they drown. The pool of water is home to many bacteria and protists that help to digest the plant's prey. Some fly larvae also live in the pool of water and eat the protists. Which two species have a relationship of mutualism?