The White-flanked Antwren is perhaps the most widespread and familiar of the antwrens, a group of small, short-tailed antbirds. It is the only antwren with bold white flank patches that contrast with otherwise dark plumage. These patches are particularly conspicuous because of this birds' habit of nervously flicking its wings to reveal the flanks. It occurs in the understory of lowland forest from Honduras south through northern South America to Bolivia and coastal eastern Brazil, although microhabitat preferences vary between regions. It often associates with mixed species flocks, feeding actively on arthropods obtained from vegetation with lunges or short sallies. The nest is a cup of dead leaves placed on a branch fork.