American Osmia species with modified facial bristles for pollen uptake
In a recent paper, Rightmyer et al. (2011) describe two new Osmia species from the southeastern United States belonging to the subgenera Melanosmia and Diceratosmia, respectively, which both possess a specialized facial pilosity composed of short and erect bristles. These bristles are used to collect pollen from nototribic flowers. At least six other Osmia species from North America have modified facial hairs, which probably have the same function (Rightmyer et al., 2011). In the Palearctic osmiine bees, a specialized facial pilosity used to collect pollen from the nototribic flowers of Lamiaceae and Antirrhineae is known to date from twelve species of Osmia (Helicosmia), four species of Osmia (Erythrosmia), three species of Hoplitis (Micreriades) and one species of Hoplitis (Hoplitis). Thus, morphological specializations for exploiting nototribic flowers have independently evolved many times in the osmiine bees.