Being one of the species with a wide distribution, striped imps have a variety of ecotypes and subspecies. One of the most divergent to the point of being considered a separate species by some are the grass imps, which are notable to inhabit bamboo forests, as well as montane pine forests. They are a bit smaller than the common form and possess longer feathers along the hind rims of their limbs. The most notable trait is their wider beard, which extends down to the base of the neck and is present on females as well.