Forest Preserve District of Cook County, Illinois
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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 surface litter.

Many foresters are coming to believe that when we plant trees we should also plant earthworms.

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