Abstract. Devillers, P. & Devillers-Terschuren, J.- Observations of the orchids of the Ophrys subfusca group in Tunisia [Natural. belges 81 (Orchid. 13) (2000):  283-297 + 8 figs]. Mediterranean Africa appears to have been a centre of radiation for orchids of section Pseudophrys of genus Ophrys. They comprise there a large number of sometimes very original forms, probably belonging to several lineages, of which some are little or not represented in the rest of the Ponto-Mediterranean basin. It is also the only region where the Pseudophrys generally exceed the Euophrys in frequency, abundance and diversity. North Africa harbours forms that seem to be intermediate between well individualised groups in Europe and Asia Minor, a particularity to be expected in a centre of differentiation. This richness in intermediate forms is particularly striking in the Ophrys fusca and O. lutea groups and has long attracted attention. In our systematic analysis of genus Ophrys, we proposed to make a distinct group within the ensemble O. iricolor-O. fusca-O. lutea for the North African plants showing characters intermediate between Ophrys fusca and O. lutea, a group comprising at least two species, O. subfusca and O. battandieri. Observations made during a recent visit to Tunisia in the spring of 1999, a favourable year for orchids, have comforted us in this approach while suggesting that the North African group was probably more diversified than we had indicated. This note summarises these observations. It re-examines the characters of the Ophrys subfusca group and those of its constituting species. Ophrys battandieri, common in coastal regions is closest, visually, to the Ophrys lutea group. Ophrys subfusca is reinterpreted as a very small-flowered species abundant in the Dorsale, including at relatively high altitudes. Ophrys numida is newly described as a species similar to O. subfusca and sharing its Tunisian stations, but with more robust plants and slightly larger flowers, in the size range of O. sicula. Ophrys aspea is also newly described as a very distinctive, large-flowered species with strongly convex lip, so far known only from limestones of Cap Bon. The limits of the Ophrys subfusca group, its probable distribution in North Africa, its potential presence in Europe, and its relations with other Pseudophrys lineages are briefly discussed.

Key-words: Orchidaceae, genus Ophrys, Ophrys lutea, Ophrys fusca, Ophrys subfusca, Ophrys numida, Ophrys aspea, Ophrys battandieri, Ophrys murbeckii, Ophrys gauthieri, Ophrys pouyannei, Ophrys lievreae, Tunisia, Dorsale.