By Staff
If you think about it worms are some of our most prevalent species here in the upper Midwest. They're everywhere – in every scoop of garden soil, stretched out all over the lawn at night and massed on the driveway after a rain.
In fact, a typical acre of ground supports an estimated one and a half million worms. It hasn't always been that way, though. All of our earthworms are aliens. If there ever were worms in the northern U.S., which is debatable, they were wiped out by the glaciers. Our worms hitched a ride over here with the early settler's imported plants and dirt used as ship ballast. Due to introductions by commercial worm farms, fishermen and gardeners we now have many species but they can be lumped into three distinct categories according to their habitat.
The generically termed garden worms live in the topsoil. The little, squirmy red worms so popular with fishermen live above ground in leaf litter and compost. Then there's the mighty nightcrawlers, or earthworms, that dig burrows deep under ground, up to six and a half feet down when escaping winter's frost.
I know you've wondered what that band or collar on the forward part of the body is about. It produces a mucus sheath to serve as a cocoon for worm embryos. Worms are hermaphroditic (boy and girl in one package) but don't self fertilize. They mate to exchange packets of sperm. As the worm slips out of the mucus sheath ova and sperm packets are deposited in the sheath, which then self seals. It's sort of like an underground bird egg. The baby worms, of which there are several, live on the nutrients in the cocoon. When the nutrients are used up the kids hatch out.
Worms don't have lungs, they absorb oxygen through the skin. That's why, to fishermen's delight, they can live several days under water. Have you ever wondered why worms can move both forward and backward while other crawly things like snakes can only go forward? Each body segment of a worm has a series of retractable bristles that serve as anchors. With the bristles providing traction, muscle stretching and contracting propels the worm in either direction. And yes, worms do have a front and back end and there is a mouth at the front, albeit hard to see in the smaller species.
Through this mouth they eat dirt. A gizzard-like organ extracts nutrients from decaying matter in the soil. Some species such as nightcrawlers also eat living organisms like bacteria, protozoa, nematodes, fungi and such. The left over dirt is excreted above ground in the little dirt pile casts we see everywhere. Gardeners and farmers cherish the worm for this soil mixing and aerating. Worms turn over up to 20 tons of soil per acre every year. Not good for forests, though. Northern forest ecosystems evolved without worms and need heavy leaf litter and rich humus. Worms convert all that good stuff into plain dirt far too fast severely impacting forest growth.
And what's up with all the dead and dieing worms on the driveway after a rainy night? Worms must stay moist to absorb oxygen, thus the slime they're coated with. Rain or even high humidity allows them to travel above ground without drying out. Then they come out and about to party and make whoopy. Nightcrawlers also gather leaves which are drug down into their burrows for future consumption. Above ground frolicking can be hazardous, though. Exposure to sunlight for more than an hour paralyzes them. Should they happen to be on a hard surface and party too hearty and don't make their way to soft soil before dawn they're in deep doo-doo.
And finally, the most oft asked worm question – if cut in half can they really regenerate into two worms? Well, not really. All the vital innards are in the front portion. If separated several bands behind the collar they sometimes survive and regenerate a new tail. As for the back half, it's toast.
Carpe diem.