25 February 2011

The 1st earthworm of the year

The warm air and the rain that came during the night had already the brought the earthworms out early this morning when I was walking to work.
This one on the wet sidewalk was indeed the 1st one I saw this year.

To commemorate this occasion, I will ask this perennial question one more time: Why do earthworms come out of the soil during and after rains?

They do so because they can come out without risking desiccation.

But because flat and wide and porous concrete surfaces were not in the original repertoire of earthworms habitats, evolution has not equipped earthworms with the ways and means necessary to deal with the rapidly dehydrating circumstances that arise once the rain stops and the sun comes out. As a result, the worms often get stranded on dry sidewalks and parking lots and die by the hundreds.


Surferboi said...

I have been searching the web for an answer to the opposite: why are so many worms here in Leesburg, VA crawling out of the ground and dying WITHOUT a heavy rain? It's been dry here for a while, and during my walks over the last 3 days, an unusual amount of worms are crawling out into the street and dying for no apparent reason. Is it the drought? Maybe they got freaked by the magnetic storm? Very curious.

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Earthworms may come out of the ground if the air humidity is high. It doesn't have to have rained.
Worms may also come out of the ground in large numbers if there have been vibrations throughout the soil, because they may perceive the vibrations as those coming from predatory moles. See the following paper: