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Mepraia is an endemic genus found in the semiarid and arid regions of north-central Chile. Until 1998, Mepraia spinolai was the only species of the genus, distributed in coastal and interior valleys from Chile between 18 degrees and 34 degrees S. However, on the basis of karyotype and morphological characters, coastal desert populations between 18 degrees and 26 degrees S were ranked as a new species, Mepraia gajardoi. Recently, genetic studies using nuclear and mitochondrial markers on Mepraia populations suggest that the geographical criterion to separate the two species should be reviewed. Mepraia species show conspicuous alary polymorphism, unique in the Triatominae subfamily. Females of both species are invariably micropterous, while males of M. spinolai can be micropterous, brachypterous or macropterous, and only brachypterous in M. gajardoi. In this study, we use geometric morphometrics analyses to compare male wings of M. spinolai and M. gajardoi from natural populations, in order to examine if these two species have diverged in alary shape. As expected, we found that brachypterous wings of both species are smaller than macropterous wings of M. spinolai. Additionally, we detected clear differences in shape on wings of M. gajardoi and M. spinolai, not attributable to allometric effects. For last, a new alary phenotype, insects with vestigial wings, was described here for the first time. In conclusion, our analyses on wings of Mepraia species separate two distinct groups consistent with the two described species. However, our findings of vestigial wings in some coastal areas of the north part of Chile cannot rule out the existence of a hybrid zone. (c) 2010 Elsevier B.V. All rights reserved.