Eight Triatoma dimidiata populations from different geographic regions were compared along with related species using traditional morphometry of head characters. A method for removing allometric change was used for the intraspecific comparisons, and scaling for the isometric change of size was used for the interspecific comparisons. The intraspecific comparison showed significant head shape differences between T. dimidiata populations correlating with geography, showing a separation between the northern, intermediate, and southern collections (more evident in females), and supporting the idea that this species includes several evolutionarily divergent populations. The positioning of one sylvatic group from Guatemala did not correlate with geography, because it was more closely related to a distinct population of Colombia. This sylvatic group was found in caves, while the Colombian specimens, although collected in houses, may have migrated from nearby caves. Evolutionary and/or ecological influences could be responsible for the head shape similarities between these two groups: a common ancestral origin of both populations or a morphological convergence caused by similar environmental pressures. The interspecific comparisons included four other regional species of the same genus, three of them belonging to the phyllosoma complex (T. pallidipennis, T. mexicana, and T. ryckmani, the latter provisionally) and the fourth one classified in the protracta complex (T. nitida). Both complexes were readily separated by their head dimensions, even after size adjustment, and our data support inclusion of T. dimidiata within the phyllosoma complex.