An epiphragm is a temporary structure which can be created by many species of shelled, air-breathing land snails, terrestrial pulmonate gastropod mollusks. Function The epiphragm is created to seal the aperture of the shell against desiccation. It is used when the snail is inactive. Most land snails are active when the humidity is high, such as after rains and at night, and become inactive during dry weather. The main feature of the epiphragm is to reduce water loss through the aperture duri… (More on Epiphragm)