Why Do Earthworms Come Out in the Rain?


Also known as megadriles, earthworms belong to the class of Oligochaeta in the Annelida phylum. Some of the common terms that people use to refer to earthworms are angleworms, night crawlers, rainworms and dew-worms. The species have multilayered clitellum and are usually have lengths of 8 to 12 feet. In present times, scientists have discovered approximately 6,000 species of megadriles. Earthworms have unique behavior, actions and characteristics. One of the distinct behaviors is that the species commonly come out in the rain. To know the truth behind this unique behavior of megadriles, it is important to have a look at some theories related to their survival instincts.


Why do earthworms come out in the rain? There are several reasons why megadriles come out in the rain such as for survival. These worms do not come out during daytime because the sunlight has harmful effects on their skin. The skin of megadriles gets dried up when the worms have been exposed to direct sunlight. To prevent exposure from sunlight, earthworms dig holes and stay underground. Some scientists agree that rainwater can lessen the supply of oxygen underground so earthworms come out in the rain to survive.

Another reason why the species come out in the rain is that megadriles take advantage of moist surface or soil to travel to other locations faster and easier. Because of humid and moist conditions after rain, earthworms will not become dehydrated even if they stay above ground for a long time.

Some scientists believe that megadriles come out in the rain because there are less predators present. There is a big chance that they can establish colonies in other areas at this time. Another theory explaining this distinct behavior of earthworms is that rainwater can cause the soil to become more acidic, which is fatal for the species.

Other Relevant Information About Megadriles

Even if megadriles have distinct behaviors and activities, the species are beneficial to farmers because the worms can improve the fertility of soil by transforming organic matter to humus. In addition, the burrowing actions of earthworms are also important to enhance soil nutrients. According to some studies done by some scientists and experts in the United States, earthworm casts are rich in potash, phosphates and nitrogen. Another benefit from this unique and interesting behavior of megadriles is that the burrowing action is opens passages as well as channels that are important to provide the water and air needed to enhance soil nutrients.

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One Response to “Why Do Earthworms Come Out in the Rain?”

  1. William says:

    I have seen worms in my planters box came out when it is filled with rainwater. When I fill that planters box with tap water they don’t come out. So I made some research and found out that rainwater contains hydrogen peroxide or H202. There are 2 molecules of oxygen in hydrogen peroxide whereas in tap water which is H2O has only one molecule of oxygen. Worms are anaerobic and died when they come out of the soil because outside the soil the oxygen we breath is O2 or has two molecule of oxygen and much warmer than when they are in the soil. Worms can not survive in aerobic environment.