The Difference Between Earthworms and Nightcrawlers

Earthworms and nightcrawlers are terms that are often used interchangeably. In reality, the two worms differ in appearance, function and when and where they are seen. Nightcrawlers, otherwise known as dew worms or garden worms, appear at night when the dew is on the grass or on sidewalks after a rain. Earthworms, also called red wigglers, are used in worm composting or vermiculture activity.

Worm composting makes use of red wiggler earthworms to turn kitchen scraps into garden compost. These voracious worms eat half their weight in organic matter each day and leave fertile black compost behind. The red wigglers grow about 4 inches long. Garden supply catalogues offer red wigglers by the number of worms or by the pound. They are shipped live when the weather is not too cold, usually from April to October.

Nightcrawlers are grayer and much larger than red wigglers. Nightcrawlers are thicker, and some have been known to grow up to 14 inches long. Nightcrawlers can be seen feeding above ground at night when the dew is on the grass or on driveways and sidewalks after a rain. Nightcrawlers burrow during the day, consuming soil and transporting nutrients from deep in the ground to areas closer to the surface. Nightcrawlers can burrow as deeply as 6.5 feet. Nightcrawlers aid in soil aeration and quality through their movements and defecation.

Nightcrawlers are popular as bait for fishing because their larger size and constant movement make them attractive to fish. Worm picking is big business in some areas, as farmers and golf courses allow people on their land at night to collect worms for purchase by recreational fishermen. Worm pickers wear head-mounted flashlights and use both hands to catch the elusive worms. The worms are sold by the dozen in tackle shops and, during fishing season, in cottage country vending machines.

Unlike nightcrawlers, red wigglers should be avoided as a source of food, especially for snakes. Biology professor and snake ethologist Lani Lyman-Henley, writing on gartersnake.info reported that red wigglers can produce coelomic fluids that are toxic to snakes. Nightcrawlers do not have the same effect. Snake owners wish they could use the red wigglers, as they are cheaper and easier to store than nightcrawlers. Nightcrawlers need to be refrigerated, while red wigglers can be kept at room temperature in kitchen compost containers.

Compost worms, or red wigglers, have different scientific names than the nightcrawler. The nightcrawler is known as the "Lumbricus terristris," while the red wiggler is one of the "Eisenia" species of worms. Each worm has its own specialized purpose and is of value to the fisherman and gardener, respectively.