Heliconius erato (above), and H. melpomene (below), a pair of Müllerian co-mimics from different sites in Ecuador and Northern Peru. Each species gains protection from the other's unpalatability. Within any site, the two species are excellent co-mimics, but major geographic differences in colour pattern have evolved within each species. This geographic diversity is extraordinary by temperate zone standards: the region (about 600km x 300km) of the Andean foothills from which all these forms within each species can be found is less extensive than New England or Great Britain.