RESUMEN
Owing to the existence of cryptic species that are difficult to distinguish morphologically, the search for new taxonomic characters and methods for identifying and classifying sand flies continues. Lutzomyia longipalpis (Lutz & Neiva, 1912) and Lutzomyia cruzi (Mangabeira, 1938) (Diptera: Psychodidae) are two such species that occur in sympatry in some regions of Mato Grosso do Sul State (MS). Twenty females and twenty males from each of the five populations of Lu. longipalpis and one population of Lu. cruzi from MS were examined. An outlying population of Lu. longipalpis from Estrela de Alagoas, State of Alagoas, was used to compare the degree of divergence among the groups in MS. Specimens were cleared, mounted on slides, identified, and measured using LAS-Leica. The principal component analysis of morphometric characters showed a high degree of variation among females, while males varied to a lower degree. The populations of Alagoas and Miranda demonstrated the greatest variation. The first region, Alagoas, is geographically distant from the others and occurs under distinctly different ecological conditions, which likely accounts for the variation. Further studies should be made to elucidate the factors that contribute to the differences found between the populations of MS.