Animal barometers are known. What is a barometer? Is the leech a living barometer?

Currently, there are more than five hundred species of animals that act as barometers in nature. Freshwater crayfish and sea crabs, sensing the approach of rain, get out on the shore. Insects, on the other hand, are trying to find shelter from the rain. A barometer is a device that measures atmospheric pressure. All types of leeches sense changes in atmospheric pressure, and with the help of this they know about the approach of rain.