INTRODUCTION In this paper we describe for the first time the life-cycle of Acotyledon paradoxα Oudemans, 1903. This species was known, so far, only from the hypopial stage and a protonymph. The discovery of the adults allows us to precise the systematic position of the genus Acotyledon and to throw light on this difficult group of Acaridae. All our material was found by the junior author in a nest of a screech owl, Otus asio, in Syracuse, New York, U.S.A. It includes numerous hypopi, protonymphs, tritonymphs and adults of both sexes. One of our protonymphs contained a completely developed hypopus identical with the other free hypopi. REVIEW OF THE LITERATURE Oudemans (1903) erected the genus Acotyledon for a new species, A. paradoxa, represented only by a single hypopus collected on a bat from Russia. This hypopus is characterized by the vestigial aspect of the suctorial plate bearing only one pair of small suckers and no conoids. Zachvatkin (1937) in his first study on Tyroglyphidae did not mention the genus Acotyledon, but in 1941, after having discovered new specimens of hypopi as wel as protonymphs of the species of Oudemans, he synonymized with Acotyledon the genera Eberhardia Oudemans (1924), Cosmoglyphus Oudemans (1932) and Myrmoglyphus Vitzthum (1935). He recognized, however, that this new complex comprised two sharply different morphological types of hypopi, one of the Acotyledon type with poorly developed suckers, the other of the Cosmoglyphus type with a normally developed suctorial plate. He included in the genus Acotyledon twelve palearctic and

Zoologische Mededelingen

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Naturalis journals & series

Fain, A., & Philips, J. R. (1978). Astigmatic mites from nests of birds of prey in the U.S.A. : IV. Description of the life-cycle of Acotyledon paradoxa Oudemans, 1903. Zoologische Mededelingen, 53(3), 29–39.