Like other species of Rhegmatorhina, the Harlequin Antbird is generally uncommon and is further remarkable for having the smallest range of any member of the genus. It is endemic to southern Amazonian Brazil, where this species is restricted to a small area west of the Rio Tapajós, and its range overlaps with that of the Pale-faced Antbird (Phlegopsis borbae). The Harlequin Antbird is restricted to lowland evergreen forest on terra firme. It is an attractive bird, with a black face and throat, a rufous throat and pale grayish-green orbital skin, whilst females generally share the same features, but also have the posterior underparts and back heavily marked with black. Considered to be a ‘professional’ antbird, in that it routinely follows army ant swarms, feeding on insects and arthropods displaced by their passage, the Harlequin Antbird is dominant over most other Thamnophilidae attending these swarms, but is displaced by Black-spotted Bare-eyes (Phlegopsis nigromaculata) and probably by Pale-faced Antbirds.