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Is it a mite?—Key feature pages

Body segmentation

a) well defined segments present

With the exception of spiders and mites, most arthropods have clearly segmented bodies, at least ventrally on the abdomen (or opisthosoma). Even beetles, which may look smooth and featureless dorsally have clear abdominal segments ventrally. Segmentation is obscure in some soft-bodied insects and in ostracods it is not apparent.

Misinterpretations allowed: Some armored mites appear to be segmented and are included here as misinterpretations. These tend to be among the smallest of the Acari
Factsheet for:Acari
Glossary:Opilioacariformes:
an obsolescent supraordinal term used for the Opilioacarida.
 (e.g., Tarsonemidae, Pygmephoroidea, Enarthronota) and are usually <0.5 mm long. The 'segments' are dorsal only: no ventral segments are present. (You can choose to disable "Allow misinterpretations" in the Preferences (gear icon) options.)

b) ring-like annulations without clear segments

Onychoporans (peripatus, velvet worms) have legs (lobopods), antennae, and the body ornamented with ring-like annulations that somewhat resemble segments.

c) false-segmentation

Some enarthronote oribatid mites have 1–3 notogastral scissures that are associated with body flexion and/or erectile setae, but probably do not represent remnants of primary segmentation. Some prostigmatic mites also appear to be segmented, especially those in the Heterostigmata (Tarsonemoidea). Mites that appear to be segmented are well sclerotized and have a series of plates dorsally, but these divisions do not extend ventrally. True segmentation is recognizable in some early derivative Endeostigmata, but these a mites are soft-bodied and unlikely to be seen as segmented except by specialists.

d) body without separate segments

Spiders, mites and some crustaceans (e.g., cladocerans) have no primary hind-body segmentation. In some insects and springtails segmentation may be obscured, and in ostracods it is not at all apparent externally.

Misinterpretations allowed: Palpigrades and some small opilionids are very lightly sclerotized and may be thought to lack segments if not closely scrutinized. (You can choose to disable "Allow misinterpretations" in the Preferences (gear icon) options.)

Feature pages