March 16, 2021

Now that it has gotten warmer all the bugs and critters in my yard have come back in full array.  I always wondered what the robins and blackbirds were eating as they canvased my yard until I read about the insects that stay just under the surface to avoid freezing during the winter.  When it begins to get warm, they emerge and then rest on the grass to warm up and gain strength before taking off in flight to find a mate.  Many of them do not make it much farther than the blades of grass as the birds devour them.  Unlike the insects who hibernate as larva, mosquitoes find animal burrows or similar shelter and enter a state of torpor to survive the cold.  Now that it is warmer, they are again on the loose and I have seen several large ones on the windowpanes of my bay window in the kitchen.  Time for the birds to go to work.

Insects are not the only thing brought out by the warmer weather.  The grubs and worms that inhabit my yard have also become active.  The recent rains have forced them out of the ground for the apparent mass suicide they tend to suffer.  When I looked online for an explanation, I found an article by Teri Balser, an associate professor of soil and ecosystem ecology at UW–Madison.  The answer starts with worms breathing through their skin.  “Oxygen from air or water passes directly from their outer cuticle into their blood vessels.”  Normally, soil has a 50/50 mix of air and water in the pore space between the soil particles.  After a rain, the soil pores and the worm burrows fill with water.  Oxygen diffuses about a thousand times slower through water than through air.  The worms cannot get enough oxygen, so they come to the surface to breathe.

Why they get lost on the surface is less clear.  Once they get out on the surface, they seem to become confused and cannot find their burrows after they dry out.  They move around trying to find safety, but those who wander onto the concrete driveways or gutters have no way to go back into the ground.  As the sun begins warming the concrete and the water dissipates, the worms dry out and die.  The three worms I found yesterday had taken refuge under my garage door.  Two appeared to have succumbed and dried out but one was still alive and wiggling.  I threw them all back in the yard, just in case.

Thoughts:  Almost every earthworm in North America came from somewhere else.  Native earthworms north of Pennsylvania were all but all but wiped out by the glaciers of the Pleistocene ice age 10,000 years ago.  Even the southern earthworms were forced to compete with the European worms brought by European settlers as early as the 1600’s.  They crossed over in root balls or the dry ballast of ships.  As the British, French, Spanish and Dutch colonized the American continent, European worms came with them.  These species thrived in the upper soils of forests and gardens, while any native earthworms remained deeper underground.  Europe’s earthworms established an empire that outlived any built by its nations.  It is odd to think the Canadian night crawlers I use for bait are descendants of immigrants.  Ironically, so are all of us.  Do the work.  Follow the science.  Change is coming and it starts with you.

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