A FEW WORDS ON WORMS

While it is still technically winter (until the spring equinox on March 20, 2018), the spring rains are here and with that comes a surprisingly large number of worms on sidewalks.  Why?  There are many hypotheses.  To fully appreciate the hypothesis, we need to delve into some worm anatomy and a bit of chemistry/physics (I’ll be gentle).

Worms get air through their skin via the process of diffusion.  Diffusion is the movement of molecules from an area of high concentration to an area of low concentration and this continues until the concentrations are equal (homeostasis).  Say WHAT?!?  Basically, there is more oxygen on the outside of the worm than inside the worm.  Oxygen is drawn across the worm’s skin and used by the cells of the body.  More oxygen is drawn across the skin and this process continues.  The funny think about oxygen is that you need a moist surface for diffusion to occur.  The worm must keep its body moist.  It does this by secreting mucus which is why worms feel “slimy/wet”.  Worms also remain in moist environments (soil).  Traveling above ground would be hazardous to their health because they would dry out and die.  Rain changes everything and makes the above ground environment suitable…until the rain stops, the sun comes out and the worm is stranded on the sidewalk…   

Some suggest that the rain drops cause vibrations like that of moles (worm predators) moving through the soil.  The idea is that the worms evacuate to the soil surface to avoid moles.  This is problematic.  Apparently, the vibrations of water striking soil are not the same as moles. 

Another hypothesis is that the worms move to the surface to avoid “drowning” in the water that is infiltrating the soil.  This is unlikely.  Worms need moisture and can survive in water.

Lastly, there is the “great worm migration” hypothesis.  The idea is that worms can’t survive for long above the soil.  When the rains come, there is a window of opportunity for worms to travel “quickly” above ground to new territories.  Why?  Likely to find a mate.  I’ll address worm mating in my next post.  And, why are there so many worms on sidewalks?  Well, I don’t know if there are more worms on the sidewalks or if there are more worms in general and we are just seeing them more easily on sidewalks.  Really, who is taking the time to look for worms in grass on rainy days?  This seems like a good research project for a kindergartener.

An interesting video on why worms come out after rains:https://www.youtube.com/watch?v=V4zhogVAuqc