Back to FAQ's About Worms
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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