The corn leafhopper, Dalbulus maidis (Delong & Wolcott) (Hemiptera: Cicadellidae), is the most important vector of maize, Zea mays L., pathogens throughout the Americas. This species originated in central Mexico, and the farthest southern latitude of the corn leafhopper' range is in Argentina. A comparison of reproductive and phenotypic traits between Argentinian and Mexican (native) populations can aid in understanding the adaptation of Argentinian populations of the same species. In this study, we compare the fecundity and body size (wing length and head width) of central Mexican D. maidis populations from low (<1,000-m) and high (>1,000-m) elevations with Argentinian D. maidis populations from low (<1,000 m) and high (>1,000 m) elevations. Argentinian populations from high elevations show higher fecundity than Mexican high elevation populations. Furthermore, Argentinian females from high elevations are larger in body size than Argentinian females from low elevations and Mexican females from low and high elevations.