Esemephe tumi, a new genus and a new species of tenebrionid beetle belonging to the myrmecophilous subfamily Cossyphodinae, is described from Peru. The subfamily is recorded from the Americas for the first time; the group is also represented by species in Africa and India. The new species is illustrated, and biological observations are givem. The new tribe Esemephini is erected, and a key to the known tribes of the Cossyphodinae is provided. A discussion of the zoogeography and phylogeny of the subfamily is presented.