The morphology of the mandibles of the alates and workers of the 8 soil-feeding genera with nasute soldiers from the Neotropical Region is studied. Three mandibular patterns are recognized : (1) Convexitermes, Atlantitermes, Araujotermes, Coatitermes, Subulitermes and Agnathotermes have mandibles with complete marginal dentition and no reduced teeth, (2) Angularitermes has mandibles with complete marginal dentition but two teeth are vestigial, and in (3) Cyronotermes the marginal dentition is incomplete. A set of other characteristics is associated with each of these mandibular patterns. Intraspecific variation are registered, either between the alate and the worker castes of all genera, as between the worker types of the dimorphic worker caste of the genera with complete and developed marginal dentition. Such dimorphism was previously unreported for the soil-feeding Nasutitermitinae; the soldier arises from one worker type.