Diversity among Lutzomyia longipalpis populations in Venezuela was characterized using 2 methods: larval mouthpart morphology-morphometry and isoenzyme electrophoresis. Analysis of the results suggested the presence of 2 morpho-genotypes. The mentum, maxillary comb, mandibular ventral teeth, and adenylate kinase and hexokinase enzyme-encoding loci suggested that a population from the northwestern Coriano System (Curarigua) is a distinct lineage within the L. longipalpis complex. Three widely separated populations from the Llanos (savanna), Andes, and northcentral Coastal Cordillera showed no significant substructure. These studies provide morphologic markers that are congruent with genetic data and suggest that the morphologic markers may be used to characterize and differentiate populations within this species complex.