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(Myrientomata), an order of primitive wingless insects (apterygotes). They are 0.5–2 mm long. In Protura, the cirri, or antennae, are completely lacking (hence their name in Russian of bessiazhkovye nasekomye [antennaeless insects]); they also have no eyes or wings. The front pair of legs is directed forward and is equipped with cutaneous sensory organs; these legs serve not for crawling but for feeling, thus replacing the cirri. The abdomen has from one to four pairs of rudimentary abdominal legs, a trait linking the Protura with the Myriopoda class. Many Protura do not have tracheae (Acerentomidae family). Protura are widely distributed; they live mainly in warm climate regions, in hidden, wet places. They develop by anamorphosis. There are more than 200 species; in the USSR there are Eosentomon silvestrii, living in pine tree stumps, and Nipponentomon, living in rocky soils in the southern Urals.