In science fiction magazines of the first half of the twentieth century, tropical environments are chaotic domains where civilised restrictions do not apply. Visitors who cross the boundary between civilisation and jungle exhibit carnal desires and violent behaviours in response to the opportunities and threats they encounter. Mysterious cities and settlements hidden in the jungle and inhabited by supernatural beings are a common feature of science fiction of  this period. The tropics are ‘torrid’ in both a human, emotional sense, as well as in the sense of Aristotle’s definition of a geographical area that is virtually uninhabitable due to the hostility of the climate (Physics, 362a33-362b29). However, by the end of  the century, the tropical jungle had been transformed in science fiction into something positive and less fearsome; a rich ecological reserve, endangered, and in need of preservation. Tropical science fiction narratives reflect a changing public understanding of the tropics, and illustrate the value of science fiction as a record of the history of changes in social and cultural values.