Nature Bulletin No. 12 April 28, 1945
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation
Most people think of earthworms only as food for robins and bait for
fishing. They are called "fishworms", "angleworms", and 'I'night
crawlers". By digging in moist, rich soil, one can usually find several
per square yard. They also may be found at night, using a flashlight
with red cellophane over the lens, because earthworms come to the
surface at night to feed on dead leaves or blades of mowed grass. Their
"saliva" is strongly alkaline and softens such vegetable matter so they
can digest it. They have no eyes nor ears but are very sensitive to touch
and light. Red light does not bother them but they cannot endure the
ultraviolet rays in daylight, which paralyzes them.
In the morning, after a heavy rain, large numbers of earthworms will be
found on sidewalks and the ground surface, where they came for air to
escape drowning. If they do not succeed soon in crawling back into
their burrows, they die.
There are many species of earthworms. The largest, the true "night
crawler", was imported into this country.--probably in earth around
shrubs and bulbs. Twenty-two species have been found in Ohio, 10 of
them some of the 19 species native to Denmark. Thirty-seven species
have been found in the British Isles. Some are quite small. Some live 10
or more years. They are composed of a large number of segments, or
rings, each having four pairs of little bristles that enable them to crawl;
and on the surface there are numerous small holes to the tiny kidneys
and other organs. The mouth end is larger; the tail end flatter.
Earthworms are the most important animals affecting the structure and
fertility of soils, particularly forest soils. They excavate many channels
in the soil, sometimes 8 feet down into the subsoil, which lets rainwater
penetrate. They bring the excavated material to the top and deposit it
around the mouth of the burrow as "castings. " Therefore, they are
mixers of the soil, as well as channellers. Charles Darwin found as
much as 36,000 pounds of castings per acre. Other scientists have found
from 75 to 300 earthworms per square yard of forest soil. Consuming
the dead leaves, blades of grass and other litter -- in the fall they pull
quantities of these down into their burrows -- they are also reducers of
Many foresters are coming to believe that when we plant trees we
should also plant earthworms.
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Update: June 2012