About Worms

Terminology

• The word "worm" is commonly applied to any member of the invertebrate/insect kingdom that is legless and has a long, soft body. The number of species of creature fitting this description is in the hundreds of thousands and can include earthworms, flatworms, parasitic worms and insects in their larval stage.
  
  

Earthworms

• The earthworm belongs to the annelid phylum and lives underground in dirt, with most species remaining under the soil except when disturbed or when rain flooding causes their environment to become suffocating.
  Earthworms crawl by expanding and contracting the muscles over the length of their bodies and by using tiny, gripping hairs. They have no sense of sight or hearing. The diet of an earthworm comes from organic nutrients found in dirt, which they consume, excreting nondigestible matter.
  
  

Other Annelids

• The rest of the annelid phylum is also made up of creatures which are commonly called "worms." This phylum includes leeches and water worms.
  Different species of leeches may live in fresh water or salt water or on land. The most commonly known leeches are parasitic worms that live off the blood of a temporary host, attaching to the skin and sucking until they are full, then falling away to digest before seeking a new host. However, many varieties of leeches are carnivores rather than parasites, consuming other, smaller invertebrates.
  Water worms are some of the less commonly known types of worms. These worms can exist in either fresh or salt water and are generally seen by human eyes only when they are being observed by marine biologists. They are more closely related to earthworms than to leeches.
  
  

Larvae

• The term "worm" is often also applied to insect larvae. Though most larvae have other names (such as "maggots" for fly larvae and "caterpillar" for butterfly), many larvae are also commonly referred to as worms. The tobacco hornworm is an example of a moth larvae that is so often encountered as a pest that it retains the name hornworm even in adulthood.
  
  

Nematoda and Flatworms

• The phylum "nematoda" includes many examples of simple worms, the best known of which are parasitic. In fact, there are more than 80,000 species of nematodes, including tapeworms, hookworms, roundworms, ringworms and other creatures that nest inside different parts of the bodily systems of larger animals (including mammals) to feed off nutrients from their hosts.
  Flatworms are the simplest of the worm phyla, unsegmented and without a body cavity or any organs. Instead, they absorb oxygen and nutrients directly into their bodies by a process of direct molecular diffusion. There are many different species of flatworm, about half of which are parasitic.