palearctic species O. avosetta is one of a few species known for lining their nest burrows with flower petals. A female might inspect several potential nests before settling in. Within a few days of mating, the female has selected a nest site and has begun to visit flowers to gather pollen and nectar for her nests; many trips are needed to complete a pollen/nectar provision mass. Once a provision mass is complete, the bee backs into the hole and lays an egg on top of the mass. Then, she creates a partition of "mud", which doubles as the back of the next cell. The process continues until she has filled the cavity. Female eggs are laid in the back of the nest and male eggs toward the front. Once a bee has finished with a nest, she plugs the entrance to the tube, and then may seek out another nest location. Within weeks of hatching, the larva has probably consumed all of its provisions and begins spinning a cocoon around itself and enters the pupal stage, and the adult matures either in the fall or winter, hibernating inside its insulatory cocoon. Most Osmia species are found in places where the temperature drops below for long durations and they are well-adapted to cold winters; chilling seems to be a requirement for maturation. Some species of mason bees are semi-voltine, meaning that they have a two-year maturation cycle, with a full year (plus) spent as a larva. Anatomy and morphology Osmia share a basic anatomy with all bees and most insects; the main functional regions being the head, thorax, and abdomen. On the head, Osmia have 3 small ocelli, two large compound eyes, antennae, and a mouth. On the thorax, Osmia have six legs and four wings. The abdomen of females contains a scopa for pollen-collecting, absent in males. Although the scopa is usually located on the legs in most bees, it lies underneath the abdomen for Osmia and other genera in the family Megachilidae. Pollination Osmia can pollinate very efficiently, which is largely attributed to their anatomy and behavior. Unlike most other bee species that collect pollen from their hind legs, female Osmia and other bees in the family Megachilidae use pollen-collecting hairs from their abdominal scopa. When Osmia transfer pollen to flowers, dry pollen falls from the scopa onto the flower's stigma, facilitating pollination at nearly every visit. Osmia typically