The flea genus Rectidigitus Holland, 1969, endemic to Papua New Guinea and Papua Province, Indonesia is reviewed as a continuation of the study of fleas in the Robert Traub flea collection deposited in the Carnegie Museum of Natural History, Pittsburgh, Pennsylvania. This paper (Part IV) is an extension of previous studies by Hastriter (2012), Hastriter and Easton (2013, Part I, Striopsylla), Hastriter (2014, Part II, Nestivalius, Orthopsylloides, and Parastivalius), and Hastriter (2015, Part III, Traubia). Rectidigitus currently contains four valid species (Mardon 1981): R. ancisus (Jordan, 1937), R. spooneri (M. Rothschild, 1934), R. szentivanyi Holland, 1969, and R. traubi Holland, 1969. The male of R. ancisus is described for the first time and the previously known distribution of this species is expanded from Morobe Province to Southern Highlands and Western Highlands Provinces. An additional four new species of Rectidigitus are described herein (R. angularis, R. claviculatus, R. dittmarae, and R. glomerospinosus). With the description of these four new species, the total number of described species in the superfamily Pygiopsylloidea in Papua Province, (Indonesia), Papua New Guinea (including Bismarck Archipelago), and the Solomon Islands is 105. An additional eight species belonging to three other flea families (Ischnopsyllidae (3), Pulicidae (3), and Leptopsyllidae (2)) bring the total number of flea taxa to 113 species (including subspecies). A key to the species of Rectidigitus is provided.