Appearance may be deceiving: Mexican sand flies (Diptera: Psychodidae: Phlebotominae) embrace a high diversity of cryptic species.

Phlebotomine sand flies stand out for their role in vector-borne diseases, having taxonomic priority in aspects of public health. Traditional identification based on morphology involves some limitations that have been corrected with the implementation of complementary methodologies such as cytochrome c oxidase subunit I barcoding and recently mass spectrometry. In Mexico, nearly 38% of sand fly species count with a molecular characterization, but additional information is still necessary for improving sand fly species delimitation. We carried out a molecular species delimitation study of sand flies distributed in the Mexican Transition Zone, between the Nearctic and Neotropical regions, with newly generated cytochrome c oxidase subunit I barcodes, and the first protein profiles created. Compelling evidence showed putative new taxa emerge from Micropygomyia aff. durani (Vargas & Diaz-Nájera) and Pintomyia Series serrana Barretto, and several cryptic species be contained within the genera Micropygomyia and Psathyromyia, which could be of biological and epidemiological interest. However, for some taxa an exhaustive taxonomic revision at the morphological and molecular levels is recommended, especially for sand flies of wide distribution in the New World.