Why do worms come out when it rains?

I have turned into a three year old again always asking the question why. Today after a rainfall at the bluff, of course, there were a tons of slimy worms scattered all over the surface of the dirt road. As a child, I remember finding interest in collecting the worms and storing these little guys in a bucket filled with dirt. This was until my mom made me put all of them back where I found them.

It is a common myth that worms come out of the ground when it rains because they might drown. This is not true. Worms breathe through gas exchange which occurs through their skin. If water has enough oxegen worms can survive in water for many days. So the question is why do these slimy friends come out when it rains? Well, since worms use oxegen to breathe through their skin, being above ground in a moist envirement allows these creatures to thrive. The sliminess and moistness on the worm is actually mucus which assists the worm with the gas exchange. Gas exchange must take place for a worm to survive After a rain a worm plays on the surface because the ground is moist.

Days when it is not raining the envirement above ground is usually to hot or dry for the worms therefore they can die when exposed to those elements. After an hour of being exposed to the light they can be parylyzed and die.  Worms also choose to come out at night because the air is cooler and the envirement tends to be moist in the evening hours. The most prominent reason for coming above ground after a rain has to do with a worms preference to mate on the surface of the ground. Interestingly, these creatures are simultaneous hermaphrodites having both sex organs. In the winter our wormy friends find a home deep in the soil below permafrost where it is warm enough to survive until it is warm again.


Adam C. Chapin said...

Good info!

Seth C. Burgess said...

Maybe we should get into vermicomposting?

Gil Burgess said...

You're unearthing just all sorts of stuff about nature. Keep it up!

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