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Urban species #083: Canadian nightcrawler Lumbricus terrestris

Scientists believe that there is no such thing as a native New England earthworm. 21000 years ago, a mile deep sheet of ice covered the whole of the region, all the way to Long Island. The ice scraped down to the bedrock, pushing soil, and any worms that might have lived in it, right to the edge of the continental shelf. When the ice receded, and animals and plants spread back to the area, it is thought that earthworms were not among them. But plants from other parts of North America, and Europe, were brought soil and all--including earthworms. One of the most common of the fifteen to twenty species of earthworms is the Canadian nightcrawler. Despite its name, the Canadian nightcrawler is native to Europe, but happens to be the large earthworm best adapted to the Northern North American climate.

Canadian nightcrawlers are nocturnal animals that spend the daytime in deep burrows. Other kinds of earthworms feed on organic material in the soil itself, while nightcrawlers emerge from their burrows at night to feed on dead leaves. They pull the leaves into their burrows and let them decay somewhat before consuming them. Other forms of detritus, including dead insects, are sometimes eaten as well.

This young individual was found on the leaf-littered surface of a flat rubber roof, under a board. (The roof is flush with the ground on one side: the worm didn't scale the walls.) When fully grown, a nightcrawler can be eight inches long or more. This species goes by a number of different common names. In Britain it is simply known as the common earthworm; in New Zealand and North America it goes by "nightcrawler," and an alternate Canadian name is "dew worm."

Outside of Europe, as an alien species, it may be contributing to the decline of some ecosystems. Ironically, in Europe it is threatened by introduced predatory flatworms from New Zealand and Australia, and soil quality in some parts of Europe is declining as a result. The important ecological role of earthworms and their contribution to soil fertility is known in large part because of Charles Darwin's research.


( 3 comments — Leave a comment )
Mar. 25th, 2006 04:41 pm (UTC)
I love worms so much! :)
Mar. 25th, 2006 04:57 pm (UTC)
I had so much fun with these guys as a kid. Part of my mom's garden was a lot of flat lava rocks on a walkway around it, and there'd be a bunch under them after a good rain (along with ants and spider and pill bugs....). Sometimes my sister and I would collect them for fishing.
Mar. 25th, 2006 05:24 pm (UTC)
nightcrawlers are thought in much of their northern american habitat to be one of the primary nature-based (i.e. nonhuman) causes of the decline of such native herbaceous woodland plants as trilliums.

they just LOVED my shaded woodland-style garden (the one where i had the trilliums) and if i went out with a flashlight at night i would often find dozens of them prowling for foodstuffs just in my little urban garden.
( 3 comments — Leave a comment )


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