Worm - Definition and Overview

For other uses, see Worm (disambiguation).

A worm is any of numerous relatively small elongated soft-bodied invertebrate animals. The most famous is the earthworm, a member of phylum Annelida, but there are hundreds of thousands of different species that live in a wide variety of habitats other than soil.

Originally, the word referred to any creeping or a crawling animal of any kind or size, such as a serpent, caterpillar, snail, or the like. Later this definition was narrowed to the modern definition which still includes several different animal groups. Major phyla include:

• Acanthocephala (spiny-headed worms)
• Annelida (segmented worms)
• Chaetognatha (arrow worms)
• Gnathostomulida (jaw worms)
• Nematoda (roundworms)
• Nematomorpha (horsehair worms)
• Nemertea (ribbonworms)
• Onychophora (velvet worms)
• Platyhelminthes (flatworms)
• Sipuncula (peanut worms)

Some other invertebrate groups may be considered worms. Many insect larvae are called worms, such as the railroad worm, glowworm, or bloodworms. Worms may also be called helminths, especially in medical terminology.

When an animal, such as a dog, is said to have worms, it means that the dog is infested with parasitic worms such as tapeworm (or the fungal ringworm).

See also

• Woodworm (the larval stage of certain wood-boring beetles)