in seven studied communities of western mexico, triatomine specimens were sympatrically collected, some with atypical morphological characteristics in contrast to pure specimens, which were presumed to be hybrids. more than 200 specimens of meccus pallidipennis and meccus longipennis with brown-yellow markings on dorsal connexival segments were collected in ahuacapán and quitupan. in la mesa, more than 60 specimens similar to meccus picturatus in most morphological characteristics (including size) were collected, although they presented a largely yellowish corium like m. pallidipennis. interfertility was proven between all of the studied wild hybrid specimens, as well as between all the experimental laboratory hybrids. two different phenotypes (m. picturatus and m. longipennis) were obtained from crosses between m. picturatus x m. picturatus and m. longipennis x m. longipennis from the three studied localities in state of nayarit as from la mesita. results support the hypothesis that the subspecific ranking of those triatomines may, therefore, be more appropriate because reproductive isolation has not been developed and complete interbreeding was recorded.