It depends on the types of worms. Some are considered insects and others are protozoa.
In this sense, it is not a ‘yes or no’ answer but a response about the difference between two types of invertebrates. The worm is an invertebrate animal that has no backbone and often shares many characteristics with insects. The distinction between some groups of worms (e,g., earthworms) hinges on whether they have true body cavities inside their gut or just pleats for folds in their wall while other identify traits lay in whether they have bristles or not and whether they can bore into the ground for food to divide eggs up from one parent]. There are three traditional sub-classes within this phylum classified as follows:
- Annelids- worms that have cylindrical, segmented bodies with a tubular cavity between each of the segments.
- Nematodes- worms that lack a tubular cavity between their segments and have round cross sections that do not resemble Earthworms or Leeches.
- Plathelminthes- worms that have flattened ventrals, dorsals, and spiral in orientation with difficult to identify traits for identification purposes without dissections.
- Nematomorpha- worms that are long, slender, many branched without any digestive tract for absorption of food and lack a gut lid but do have an outer layer of muscles used to propel themselves through water by undulating their body like sidewinding snakes.
- Gastrotricha- worm that are microscopic with dorsal adhesive field used to attach themselves to substrates
- Kinorhyncha- worm that are similar to free living flatworms but have bristles instead of cilia for movement and a sensory organ known as a statocyst.
- Loricifera- microscopic worms that have both bristles and cilia for movement through water and feed on bacterium while being free living. They have a carapace made up of microscopic plates called scales
- Priapulida- worm with an anterior proboscis used to chew into other invertebrates or enter their body cavities for feeding purposes while the posterior segment has 2-3 fingerlike projections that hug the walls of the gut and may leave slime to make movement easier.
- Acanthocephala- worm that parasitize invertebrate animals such as aquatic insects, crustaceans, molluscs or echinoderms (marine invertebrates) to obtain food while leaving their hosts alive because they do not kill their hosts.
- Cycliophora- microscopic worm with a mouth surrounded by tentacles for feeding purposes while lacking subpharyngeal glands, are rarely found in aquatic habitats, have an incomplete digestive tract but highly developed neurochord which is used to detect light or other stimuli.