Worm

 ( Animal Common Names ) 

Worms are many different distantly related bilateria that typically have a long cylindrical tube-like body, no limbs, and usually no eyes.

Worms vary in size from microscopic to over in length for marine polychaete worms (bristle worms); for the African giant earthworm, Microchaetus rappi;; and for the marine nemertean worm (bootlace worm), Lineus longissimus.

Various types of worm occupy a small variety of parasitism niches, living inside the bodies of other animals. Free-living worm species do not live on land but instead live in marine or freshwater environments or underground by burrowing.

In biology, "worm" refers to an obsolete taxon, Vermes, used by Carl Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate , now seen to be paraphyletic. The name stems from the Old English word . Most animals called "worms" are , but the term is also used for the amphibian and the anguis fragilis Anguis, a legless burrowing lizard. Invertebrate animals commonly called "worms" include , , , , Chaetognatha, Priapulida, and insect such as grubs and .

The term "helminth" is sometimes used to refer to parasitic worms. The term is more commonly used in medicine, and usually refers to roundworms and tapeworms.

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History In taxonomy, "worm" refers to an obsolete grouping, Vermes, used by Carl Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate , now seen to be polyphyletic. In 1758, Linnaeus created the first hierarchical classification in his Systema Naturae. In his original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the chordate, while his Insecta (which included the crustaceans and arachnids) and Vermes have been renamed or broken up. The process was begun in 1793 by Lamarck, who called the Vermes une espèce de chaos (a sort of chaos) and split the group into three new phyla, worms, echinoderms, and polyps (which contained corals and jellyfish). By 1809, in his Philosophie Zoologique, Lamarck had created 9 phyla apart from vertebrates (where he still had 4 phyla: mammals, birds, reptiles, and fish) and molluscs, namely , annelids, crustaceans, arachnids, insects, worms, Radiata, polyps, and .

Stephen Jay Gould (2025). 9780674061675, Harvard University Press. . ISBN 9780674061675

Chordates are remarkably wormlike by ancestry.

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Informal grouping In the 13th century, worms were recognized in Europe as part of the category of reptiles that consisted of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians", as recorded by Vincent of Beauvais in his Mirror of Nature.

Mary Franklin-Brown (2025). 9780226260709, The University of Chicago Press. ISBN 9780226260709

In everyday language, the term worm is also applied to various other living forms such as , , , , (teredo worms), or even some vertebrates (creatures with a backbone) such as Anguis fragilis and caecilians. Worms include several groups. The three main phyla are:

• Platyhelminthes, includes the , Cestoda, and Trematoda. They have a flat, ribbon- or leaf-shaped body with a pair of eyes at the front. Some are parasites.
• Nematode, contains the threadworms, and other Nematode. Threadworms may be microscopic, such as the vinegar eelworm, or more than 1-metre (3 feet) long. They are found in damp earth, moss, decaying substances, fresh water, or salt water. Some roundworms are also parasites: the Guinea worm, for example, gets under the skin of the feet and legs of people living in tropical countries.
• Annelid, consists of the segmented worms, with bodies divided into segments or rings. Among these worms are the and the Polychaete of the sea.

Familiar worms include the , members of phylum Annelida. Other invertebrate groups may be called worms, especially colloquially. In particular, many unrelated insect are called "worms", such as the railroad worm, woodworm, glowworm, Midge, butterworm, Geometer moth, mealworm, silkworm, and Woolly worm.

Worms may also be called , particularly in medical terminology when referring to , especially the Nematoda (roundworms) and Cestoda (tapeworms). Hence, "helminthology" is the study of parasitic worms. When a human or an animal, such as a dog or horse, is said to "have worms", it means that it is infested with , typically nematode or . Deworming is a method to kill off the worms that have infected a human or animal by giving anthelmintic drugs.

"Ringworm" is not a worm at all, but a skin fungus.

Lobopodia are an informal grouping of extinct Panarthropoda from the Cambrian to the Carboniferous that are often called worms or "worm-like animals" despite having had legs in the form of stubby lobopods. Likewise, the extant Onychophora are sometimes called velvet worms despite possessing stubby legs.

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Society and culture Wyrm was the Old English term for snake ("serpents") and mythical European dragon. "Worm" has also been used as animal epithet to describe a cowardly, weak or pitiable person.

Worms can also be farmed for the production of nutrient-rich vermicompost.

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See also

• Helminthology
• Nematology
• Sea worm, lists various types of marine worms
• Worm cast
• Worm charming
• Vermeology

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Explanatory notes

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