It lists, revises and illustrates the species, including also some species which have previously been reported from the Galapagos, but of which the occurence in the Archipelago is now recognized dubious or spurious. It summarizes and gathers the most significant taxonomy information on the species: the synonymies are given and subsequent citations by other authors are referenced; the complete original descriptions are cited and the type material, when available, is illustrated in colour, also for the main synonyms; more detailed diagnoses are given for the species known by an old description often made in Latin; additional material examined is thoroughly cited and sometimes figured; data on geographical distribution and habitat of the species are also summarized.

Edition: 1995