- 1The crabs belonging to the genus Sesarma show a wide range of variation in habits and in the conditions under which they live. S. meinerti is a species that has largely adopted terrestrial habits. A colony of the crabs was found at Beira, living on dry ground near mangrove-swamps. The habits of the species are described.
- 2An attempt has been made to show that the colour of S. meinerti has an aposematic function. The vivid colour of the crab, its aggressive behaviour and power of self-defence, its tough physique and well-developed power of regeneration, and the relative freedom from the persecution of enemies in which it lives, all point to this conclusion.
- 3The boldness of the species and its ability to defend itself from attack have been adopted in response to the requirements of a more or less terrestrial mode of life, and the aposematic coloration is correlated with the exigencies of this habitat; conspicuousness being useful to the ciabs. the origin and development of the warning colours are to be explained by the operation of natural selection.