Mydrosoma sabarensis sp. nov. (Figs. 1 –8, 9 e) Diagnosis. Mydrosoma sabarensis sp. n. has some of the major diagnostic features of diphaglossine bees, such as a reduced pterostigma, which is much shorter than the prestigma. In the female, F 1 is longer than F 2 but, as normal in Dissoglotini, not petiolate and less than twice as long as the other flagellomeres. In both sexes, the glossa is only moderately bifid, resembling the bilobed condition of other colletid (and other Dissoglottini) bees. The size and general pilosity pattern of this new species (Figs. 2–3; 6–7) and some details, such as presence of the stipital brushes (Fig. 4, see below), 2 nd submarginal cell smaller than 3 rd, long tarsal claws and patch of plumose hairs on latero-ventral surface of T 1, resemble M. fallax (Moure, 1953). This species was previously considered to belong to Ptiloglossidia and is known only from the Argentinean province of Salta. It can be distinguished from this species, however, by the following characters. In both sexes: preoccipital ridge present (more strongly developed in males) (absent in M. fallax); metapostnotum dull microreticulate, striate basally (in female, only laterally) (shiny microreticulate, not striate in M. fallax); arolia present (absent in M. fallax). In female: longitudinal midline of clypeus punctate throughout (smooth and shiny almost to the apical margin in M. fallax); mesosoma with white, transverse, hair band anteriorly, fuscous elsewhere (completely fuscous dorsally, white on ventro-lateral portion of mesepisternum in M. fallax); basitibial plate not delimited by carinae, its surface completely hidden by flat apressed hairs (in M. fallax, delimited posteriorly by carina, only partially hidden by thin, semi-erect hairs for most of surface); pilosity on front margin of hind tibia fuscous, composed of relatively long, densely plumose hairs (white, composed of long hairs, with short branches restricted to their apical half in M. fallax). In male: frons, vertex and most of gena blackish brown (head ...