September 29, 2023
During the last Ice Age, when glaciers scrubbed the surface of our landscape clean, any earthworms that had been living in New England were completely irradicated. Most of the worms living here now originated from either Europe or Asia and were likely brought here inadvertently in the dirt that was used as ballasts in the hull of ships exploring the “New World.” Some worms have also undoubtably arrived more recently in the root balls of imported plants. Whether intentionally imported, or as stowaways, all earthworms in New England are now considered “nonnative and invasive.” But seriously, aren’t we all?
The rain of the past few days has brought an abundance of wrigglers to the surface, which makes our chickens giddy and the pigs exuberant with all the foraging possibilities. Whatever humans may think about earthworms, our chickens and pigs consider them “swoon worthy” delicacies.
Common wisdom used to tell us that worms emerged after a heavy rain because their subterranean tunnels were flooded - but it turns out, that might not be true. Worms can survive for several days completely submerged underwater, so it’s unlikely that having their tunnels briefly flooded is really much of a problem.
Some researchers now believe worms come out after it rains simply because they can. Normally, they can’t survive on the surface because it’s too dry. After a good soaking rain, though, the surface is finally a hospitable place for them to hang out, find a mate, and to travel to far flung places (like the other side of the driveway). Worms have both male and female reproductive organs, but they can’t inseminate themselves. They need to find another worm of the same species, and after they impregnate each other, they each return to their burrows and eventually drop their eggs. It must be exponentially easier for a worm to search for and find a suitable mate above ground, but above ground is only an option for them after a soaking rain.
There is also the possibility that the sound of rain and the vibrations it causes sounds like a mole in hot pursuit, causing the worms to flee to the surface. There is, in fact, a long tradition of “worm charming” where people rub sticks together to create a mole like vibration in the soil, in order to collect worms for fishing. I’m sorry but I need some convincing on this one. If all it takes to get earthworms to come to the surface is a vibration - surely the pigs would have figured out how to shimmy and shake long ago.