t
insects
high
high
Small size and obscure segmentationsegmentation:
in mites distinct external segments have been lost but remnants of segmentation may be represented by hysterosomal folds or transverse arrays of setae and other cuticular sense organs. In theory, all chelicerates have a prosoma composed of 6 segments (cheliceral, pedipalpal, and four leg-bearing segments = body segments I-VI). Ventrally the positions of the prosomal segments can be identified by the insertions of their appendages, but dorsally they are obscured. The opisthosoma is thought to comprise an additional 12-13 segments (body segments VII-XVIII or XIX), but appears to be somewhat to much reduced in most mites, except possibly Opilioacarida. In early derivative Acariformes (e.g., many Endeostigmata), hysterosomal folds are thought to represent segmentation and in the Grandjean system are designated (from the sejugal furrow to the anus): C, D, E, F, H, PS AD, AN, PA. There is disagreement in the literature over the origin of 'segments' C and D. Adherents of Grandjean consider them to be opisthosomatic (with C probably representing a fusion of the pregenital [body segment VII] and genital [VIII] segments). Others believe that C and D are the dorsal regions of the last two prosomal segments that bear leggs III and IV (i.e., body segments V & VI).
in some (e.g., scale insect crawlers). Insects can usually be distinguished from mites by their antennae, compound eyes, wings, or clear segmentationsegmentation:
in mites distinct external segments have been lost but remnants of segmentation may be represented by hysterosomal folds or transverse arrays of setae and other cuticular sense organs. In theory, all chelicerates have a prosoma composed of 6 segments (cheliceral, pedipalpal, and four leg-bearing segments = body segments I-VI). Ventrally the positions of the prosomal segments can be identified by the insertions of their appendages, but dorsally they are obscured. The opisthosoma is thought to comprise an additional 12-13 segments (body segments VII-XVIII or XIX), but appears to be somewhat to much reduced in most mites, except possibly Opilioacarida. In early derivative Acariformes (e.g., many Endeostigmata), hysterosomal folds are thought to represent segmentation and in the Grandjean system are designated (from the sejugal furrow to the anus): C, D, E, F, H, PS AD, AN, PA. There is disagreement in the literature over the origin of 'segments' C and D. Adherents of Grandjean consider them to be opisthosomatic (with C probably representing a fusion of the pregenital [body segment VII] and genital [VIII] segments). Others believe that C and D are the dorsal regions of the last two prosomal segments that bear leggs III and IV (i.e., body segments V & VI).
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Normal adult length: usually >3 mm (range 0.6 to greater than 100 mm)
Bodybody:
the idiosoma of mites.
tagmata: head, thorax, abdomen
Eyes: various–absent, compound, ocelliocellus:
(pl. ocelli) a simple eye. Mites with eyes usually have one or two pairs of lateral ocelli, but some Opilioacarida have three pairs. Additionally, some acariform mites have one or two median ocelli on the underside of the naso.
Antennae: present, variously formed
Mouthparts: mandible, maxillae, labium, labrum, maxillary and labial palps usually distinct
Legs: 3 thoracic pairs
Distinguishing features: wings (when present); hexapodhexapod:
with three pairs of legs (i.e. 6 legs), as in the larvae of mites or the larviform stages of others.
thorax, head with antennae, compound eyes.
Comments: Insects have a head with antennae (and often compound eyes); a thorax with 3 pairs of legs (and often 1–2 pairs of wings); and an abdomen that usually lacks styli, but may have an ovipositorovipositor:
an extrusible organ for laying eggs. Female oribatids have a well developed ovipositor that ends in three finger-like projections. Ovipositors are less well developed or absent in other mites.
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lots
Author: David E. Walter
Content last updated Sept. 2006, unless indicated otherwise
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