The 36 described species of North and Central American Leptohyphes are discussed, and synonymies and other pertinent data are presented for all. Characters allow the North and Central American nymphs to be placed in species-groups; L. dicinctus and L. melanobranchus in the dicinctus-group, and all other described nymphs in the apache-group. Accounts are given for the 27 valid species known from the nymphal stage, including an illustrated key, synonymies, description or diagnosis, distribution and new collection records, and maps. L. baumanni is regarded as a synonym of L. mirus, L. consortis of L. sabinas, L. lumas of L. hispidus, and L. phalarobranchus of L. packeri. L. michaeli, L. paraguttatus, L. succinus, and L. vescus are described from nymphs collected in Texas; L. piraticus, L. vulturnus, and L. zelus from nymphs collected in Honduras.