Islands are simplified and isolated ecosystems that have been used to study ecological and evolutionary process. An important study site is the The Alcatrazes Archipelago; its main island is forested and occupied by marine birds and endemic species of terrestrial vertebrates. Records of specie richness are useful to assess the degree of habitat isolation and resilience, both relevant to practical of conservation. The pioneering registers of Lüderwaldt and Fonseca in 1923 cited seven species of butterflies. We found only three of them and found eight and two new occurrences during 1993- 1994 and 2011 expeditions, respectively. Alcatrazes island has only 18 species of butterflies known against 538 species of continental coastline. This low richness is derived from hard physical conditions of island, hindering the colonization. The Alcatrazes butterflies have good power of flight dispersal and feed on plants of secondary vegetation near-coastal habitats; its populations and community changed in short time space.