Boa is a monotypic genus, represented by the species Boa constrictor. This snake has been reported to grow to a maximum of 14 feet (4.3 m) in length. Numerous subspecies are currently recognised.
Northern Mexico through Central America (Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica and Panama) to South America north of 35°S (Colombia, Ecuador, Peru, Venezuela, Guyana, Suriname, French Guiana, Brazil, Bolivia, Uruguay and Argentina. Also in the Lesser Antilles (Dominica and St. Lucia), on San Andrés, Providencia and many other islands along the coasts of Mexico and Central and South America.
Kluge (1991) moved the genera Sanzinia and Acrantophis into Boa, based on a phylogeny derived from morphological characters. However, it has since been shown that the Malagasy boids and Boa constrictor do not form a monophyletic group, and the lumping of Sanzinia, Acrantophis and Boa was, therefore, an error. These snakes are therefore correctly represented in their own genera: Sanzinia and Acrantophis.
To add further to the naming confusion, many species of snake in the family Boidae are known colloquially as "boas" and all are constrictors. Also, more than a few subspecies of B. constrictor are recognized, several of which have distinct common names.