Peramphithoe femorata is a species of amphipod crustacean in the family Ampithoidae. It is a herbivore and constructs a tubular nest-like home on a blade of the sporophyte of the giant kelp Macrocystis pyrifera. This home is made by rolling the sides of the blade together and securing them with silk. As the kelp blade grows, so the nest is advanced down the blade towards the base, approximately keeping pace with the algal growth.