The new species Cupiennius chapanensis is described from a mangrove forest in the coastal regions of Chiapas, Mexico. The most noticeable characteristic of the species is the bright red coloration of the chelicerae, given by a covering of long setae on the anterior surface
because of this coloration, it has been previously confused with Phoneutria fera Perty 1833. It is generally similar to Cupiennius getazi Simon 1891, but lacks the spotted pattern on the ventral surface of the femora, together with other differences in genitalic morphology. Cupiennius salei Keyserling 1877 was also found on the same forest during the wet season, while C. chiapanensis appeared in the dry season. Adults of both species were never collected at the same time. This is also the first record of C. salei at the sea level, being previously considered a highland species.