Nature Notes

Worm Count

April 15, 2011
a person holding an insect

One of the signs of Spring, after a heavy rain, is the appearance of earthworms on blacktop, sidewalk, driveways and parking lots. Do you think that they were washed out of their holes, tried to escape the ‘flood’ on their own, or, like surfers, were trying to catch the ‘big wave’? Maybe they signed up for a ‘cruise to nowhere’ scam.

Sometimes there seems to be hundreds of worms, some crawling ever so slowly, some not moving at all. We at The Nature Place were curious about the ‘hundreds’ number bandied about (as we are curious about many things that make people wonder). So we recently counted the washed up worms on the blacktop driveway leading up to our winter office: Exactly 103!

Rainy Day Worm

We know that worms would not readily fall for a ‘cruise to nowhere’ scam. We did some actual research into this worm/water phenomenon and came up with some interesting information:

A. Worms cannot drown, they do not have lungs, they breathe through their skin which has to stay moist. They can live several days submerged in water.
B. Worms will drown if they stay down in their holes because there will not be enough dissolved oxygen in the water for them to breath.
C. Worms come out of their holes during a rain because the sound/vibration/rhythm of the raindrops reminds them of the pattern of sound that moles will make when digging through the soil looking for worms to eat. The worms surface to get away from the imagined mole.
D. Charles Darwin, who wrote a whole book about worms, suggested that it is only the already-sick worms that get flushed out of their holes.
E. Worms come out in the rain because all of the moisture makes it easier for them to move about.
F. Worms come out during and after a heavy rain to find a mate.
G. A rebuttal to this is that most species of worms mate below the ground, not on the earth’s surface.
These are some theories. Will we ever really know what makes worms come out during/after a rain storm? Maybe, maybe not, but it’s nice to still have some mystery surrounding simple things. For now, let’s just go outside after a rainstorm and be amazed.