The region which forms the field of these studies lies between Trinidad and the Goajira-peninsula, off the northcoast of South America, comprising of seventeen islands or island-groups with a total area of about 2000 square kilometers. It is a part of the Venezuelan Republic, excepting Curaçao, Aruba and Bonaire, which is Netherlands territory. The total number of inhabitants can be estimated at 164000, chiefly confined to Margarita (70000), Curaçao (61000), Aruba (24000), Bonaire (5500) and Coche (3000). This region was visited in 1936 and 1937 with the main object of studying the land and freshwaterfauna, excluding birds and the greater part of the insects. For comparison some parts of the adjacent continent were also visited.