Genera of Gymnodamaeidae (Acari: Oribatida: Plateremaeoidea) of Canada, with notes on some nomenclatorial problems Author Walter, David Evans text Zootaxa 2009 2206 23 44 journal article 10.5281/zenodo.189740 8dc3930d-f5da-496f-a86f-f0da1543811a 1175-5326 189740 Adrodamaeus magnisetosus ( Ewing, 1909 ) ( Figs. 9–14 ) Damaeus magnisetosus Ewing, 1909 Heterodamaeus magnisetosus ( Ewing, 1909 ) ( Ewing 1917 ) Adrodamaeus magnisetosus ( Ewing, 1909 ) ( Paschoal 1984 , Marshall et al. 1987 , Subías 2004 ) Material examined : CANADA , ONTARIO: 2 females , Burley Campground, Lake Huron Pinery Provincial Park, 15.viii.1974 , E.E. Lindquist, ex moss pads on sand dunes; 7 adults , Eganville, Shaw Woods Nature Reserve; 20. v. and 30.ix.1993 ; B. Bissett; ex mixed forest litter; one adult, St Lawrence Islands National Park, Grenadier Island, 8–9 July 1975 , D. Spaner; 2 adults , F-site Azilda, 46.31.51N, 81.6.10E, ex moss and birch litter, 15.vii.1997 , M St John & G. Bagatto, all in the CNC ; 3 adults , Shaw Woods Nature Reserve ( 46.63N , 77.07E ), 30.ix.1993 , VB138-93, V. Behan, in PMAE .IZ. Comments : Most Gymnodamaeidae have a large, cup-like tectum on trochanters III and IV that protects the trochanteral-femoral joint; however, species of Adrodamaeus have similar retrotecta protecting their distal leg joints as well ( Figs. 13–14 ). Since predators of adult oribatid mites often attack these mites at their leg joints, snipping off legs and penetrating to the hemolymph ( Molleman & Walter 2001 ), it seems likely that retrotecta evolved in response to predation pressure. This genus is similar to Arthrodamaeus Grandjean, 1954 a (see Bayartogtokh & Weigmann 2005 ) and may be a junior synonym (G. Weigmann, Institute for Zoology, Freie Universitaet Berlin, pers. comm.).