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Frequently Asked Questions About Earthworms
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Ecology

Q. Where did our earthworms come from?

A. Experts believe most native species were wiped out wherever glaciers covered the land. Most earthworms we see today were imported mainly from Europe by early settlers. The worms or worm cocoons traveled in the rootstocks of plants brought by the settlers from their homelands. Europeans added soil, with its earthworms or worm cocoons, to ships for ballast. Once anchored in North American harbors, ships released their ballast -and living worms, who found new homes.

Q. What do earthworms eat?

A. Earthworms eat dirt! Their nutrition comes from things in soil, such as decaying roots and leaves. Animal manures are an important food source for earthworms. They eat living organisms such as nematodes, protozoans, rotifers, bacteria, fungi in soil. Worms will also feed on the decomposing remains of other animals.

Q. How do worms eat?

A. They don't have teeth but they have strong mouth muscles. Dew worms or nightcrawlers often surface at night to pull fallen leaves down into their burrow. When the leaf softens a little they pull off small bits to munch on. Worms also "swallow" soil as they burrow.

Q. How much do earthworms eat in one day?

A. They can consume up to one third of their own body weight in a day.

Q. Why do earthworms stay underground and seldom come out of the soil?

A. Darkness lets them avoid being dried out by the sun. If their skin dries out, they can no longer breathe. Light paralyzes them if they're in it more than an hour. Then they can't move back to the safety of the soil.

Q. Why do worms come onto driveways and sidewalks when it rains?

A. Dr. Dennis Linden, Cindy Hale, and other worm experts say that worms do NOT surface to avoid drowning. In fact, they come to the surface during rains (especially in the spring) so they can move overland. The temporarily wet conditions give worms a chance to move safely to new places. Since worms breathe through their skin, the skin must stay wet in order for the oxygen to pass through it. After rain or during high humidity are safe times for worms to move around without dehydrating. It is true that, without oxygen, worms will suffocate. But earthworms can survive for several weeks under water, providing there is sufficient oxygen in the water to support them.

Q. Do earthworms come to the surface after heavy rains to avoid drowning?

A. Not exactly. Earthworms can survive for several weeks under water providing there is sufficient oxygen in the water to support them. They surface as a response to high relative humidity after rain because they can move around safely without drying out.

Q. How can I tell if there are earthworms in the soil?

A. When trying to find evidence of earthworms, look at the soil surface first. Earthworms often leave small piles or pellets of soil on the surface. Dig a spadeful of soil and sort through it for earthworms. Experience will also allow you to find cocoons. While you are digging, always watch for evidence of large burrows with "slickened" sidewalls. These may indicate the presence of nightcrawlers.

Q. Why do robins tug at earthworms in the soil?

A. Worms use the many tiny bristles or setae on each of their body rings to help them crawl as well as to anchor themselves firmly in their burrows. The robin has to tug because the worm is gripping the soil!

Q. Can earthworms survive freezing?

A. If frozen, they will die. Earthworms fall into the category of freeze-avoiding invertebrates. Some adults survive freezing temperatures by going below the frost line in winter to "sleep." Earthworm cocoons, however, are much more tolerant to freezing and worm eggs within a cocoon survive deep in the soil over winter to hatch in the spring when conditions are right.

Q. When are worms most active?

A. In the fall and spring. Cool temperatures of 50, 60, 70 degrees F and moist conditions are best for earthworms. Earthworms aren't active when it's cold or dry.

Q. What do earthworms do when it gets too cold, too hot, or too dry?

A. Earthworms escape by either burrowing deeply into the soil (up to about 6 feet or 2 meters), or entering a reduced metabolic state known as estivation. Estivation is a form of hibernation that takes place when temperatures get too hot or too dry for earthworms. When conditions are favorable, the worms will emerge and resume normal activities.

Q. What happens during estivation?

A. Each worm curls up into a tight ball deep in the soil and slows down its metabolism and bodily functions to survive high heat and drought.

Q. What are some earthworm enemies?

A. Snakes, birds, moles, toads and even foxes are known to eat earthworms. Beetles, centipedes, leeches, slugs and flatworms also feed on earthworms. Some types of mites parasitize earthworm cocoons or the worms themselves.

 

 

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