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Acari, mites

[R] Small-sized. Their body (the idiosoma) is composed of the propodosoma, bearing the 1st 2 pairs of legs, and of the hysterosoma, which bears the last 2 (*) .
Development is punctuated by a series of moults. The Tetranychidae develop from egg to adult through active six-legged larval, and eight-legged protonymphal and deutonymphal stages (*) .
The development cycle of Eriophyidae includes only 2 active nymphal stages.
In the Tarsonemidae, there is only 1 six-legged larval stage, which is followed by an immobile stage: the pupa.
The Tetranychidae and the Eriophyidae enter a state of diapause during the winter. In the Eriophyidae, female summer forms are called "protogynes" and female winter forms "deutogynes". The Tarsonemidae do not possess any specific winter form.
Reproduction usually is sexual. Most mites are oviparous.
Mites show extremely varied feeding habits. Some of them are haematophagous, for example ticks, which bite the vertebrates, while others are detriophagous and play an important role in the recycling of organic matter. Finally, some are predators of insects and mites.
Phytophagous mites belong mainly to the order Prostigmata. The most important representatives of this order are the Tetranychoidea, the Eriophyidae and the Tarsonemidae.
They are small-sized (less than 1 mm long), soft and provided with stylet- or hook-like chelicerae, simple palps, sometimes an internal respiratory system (which includes paired stigmata situated at the base of the chelicerae, the gnathosoma or at the humeral angles of the opisthosoma), genital and anal orifices adjacent to the ventral face of the opisthosoma.

[R] Images

* Mites (INRA)
1: gnathosoma.
a: chelicera; b: pedipalp.
2: prosoma (prodorsum).
3: opisthosoma.
2 + 3: idiosoma.

* Tetranychidae: development cycle (INRA)
a: egg; b: 6-legged nymph; c: protochrysalis; d: protonymph; e: deutochrysalis; f: deutonymph; g: imagochrysalis; h: female adult; i; male adult.

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