Bridwell (1946) used Bruchus arizonensis Schaeffer as type of the genus when he described Neltumius Bridwell in a key. Bradley (1947) transferred Bruchus gibbithorax Schaeffer and B. texanus Schaeffer into Neltumius. We describe Neltumius dospatrias Romero and Johnson, a new species from Mexico and the U.S.A. related to N. texanus. We update the distributions of the four species, list the known hosts of each species, figure the male genitalia, and key the species. Neltumius is an especially interesting genus of bruchids because its larvae feed in seeds of very different hosts, Prosopis L. (Fabaceae) and Condalia Cav. (Rhamnaceae).