A new species of Rallicola Johnston and Harrison (Phthiraptera: Philopteridae) is described from lice collected from a series of Ruddy Woodcreepers Dendrocincla homochroa (Aves: Dendrocolaptinae) in Campeche, Mexico. Rallicola deckeri is easily recognized by the unique shape of the mesosome in the male and by the pattern of divided sternites on the female.