This small antwren occurs in western Amazonia. A 2025 study treated the former garbei group, once included in the Long-winged Antwren, as a separate species. The pre-split account describes foraging in the forest mid-story, sometimes in mixed-species flocks.
The pre-split Long-winged Antwren account describes males as gray with a black bib, white wing bars, and a narrow white tail tip. Females have brownish upperparts and brown to rufous-brown underparts.
The pre-split species account says it forages in the forest mid-story, sometimes with mixed-species flocks. An Acre bird guide lists forest with palms or bamboo, alluvial forest, and submontane evergreen forest for the local form then named M. l. garbei.
An extinction-risk assessment has not been added yet.