Abstract. Delforge, P.- Remarks on the late flowering Ophrys fuciflora of the Southern Italian peninsula and description of Ophrys posidonia sp. nova [Natural. belges 81 (Orchid. 13) (2000): 157-175 + 8 figs]. The problematics of the late flowering Ophrys fuciflora with small flowers from Southern Italy and southern Alpine range (France, Switzerland) is evoked. Besides O. fuciflora s. str., it seems possible to delimite five taxa corresponding more or less to that definition, on which three are formally named, O. elatior, O. gracilis, and O. tetraloniae. Because of nomenclatural uncertainties and the lack of accurate diagnoses, those five taxa have been frequently considered as a single one and named, in turn, O. serotina nom. illeg., O. fuciflora vel holoseric(e)a subsp. gracilis, O. elatior or O. tetraloniae. Personnal research in Italy, Germany and South-East France has confirmed O. gracilis as a well delimited species, present in the Italian peninsula at least from Basilicata to Tuscana; it is a member of the O. fuciflora group and not directly related to O. tetraloniae nor O. elatior, species of the O. fuciflora complex, characterized notably by a late flowering period, and a labellum with an inconstant but nevertheless complete band of pilosity along its sides and with a rather frequent ÒscolopaxoidÓ structure. The presence of O. gracilis in South-East France, notably in Drme, is asserted. O. elatior, a very late flowering species, seems to be present only in the Rhine valley (Germany and Alsace), south of Basle, and in the Rhone basin; the O. tetraloniae distribution seems also limited to Istria and adjacent regions; the presence of both species in Italy, particularly in the Central and Southern Apennines, is highly questionable. Besides O. gracilis, two other Italian taxa have been confused with O. elatior or O. tetraloniae. The first one, which is perhaps O. serotina Rolli ex Cortesi nom. illeg., seems sometimes indistinguishable from O. fuciflora, sometimes rather well separated by a little later flowering period, smaller floral dimensions, and more polymorphic labellum shape; it is present at least in Central and Northern Italy as well as in the upper Rhone basin (SE France, W Switzerland) where it is currently but erroneously considered as O. elatior or as hybrid or transitionnal forms between O. fuciflora and O. scolopax. The last taxon from Southern Italy, named till now O. gracilis, O. elatior or O. tetraloniae, is a very late flowering species, member of the O. tetraloniae group, distinguishable notably by its floral structure and colouring system; it is described here as Ophrys posidonia sp. nov.
Key-Words: Orchidaceae, genus Ophrys, Ophrys fuciflora complex, Ophrys posidonia sp. nova, Ophrys elatior, O. gracilis, O. serotina, O. tetraloniae. Flora of Italy, flora of France, flora of Switzerland.