Mason bee

Unlike honey bees (Apis) or bumblebees (Bombus), Osmia species are solitary; every female is fertile and makes her own nest, and no worker bees for these species exist. They do not excavate their own nests. The material used for the cell can be clay, mud, grit, or chewed plant tissue. The 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. 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 three 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 pollinate early spring flowers in the family Rosaceae, and will even forage under poor weather conditions. Some farmers currently manage populations of Osmia to facilitate efficient pollination on their farms. However, using non-native Osmia species as managed pollinators has ignited the spread of disease, introducing invasive bee species that increase competition for native bees. In some areas, native Osmia species are in decline as of 2020; practices to minimize the impact of non-native pollinators on wild species include prioritizing the use of native bee species, raising local bee populations, and enforcing parasite/disease screening. ==Management==

Solitary bees produce neither honey nor beeswax. They are immune from acarine and Varroa mites, but have their own unique parasites, pests, and diseases. The nesting habits of many Osmia species lend themselves to easy cultivation, and a number of Osmia species are commercially propagated in different parts of the world to improve pollination in fruit and nut production. Commercial pollinators include O. lignaria, O. bicornis, O. cornuta, O. cornifrons, O. ribifloris, and O. californica. They are used both as an alternative to and as an augmentation for European honey bees. Mason bees used for orchard and other agricultural applications are all readily attracted to nesting holes – reeds, paper tubes, nesting trays, or drilled blocks of wood; in their dormant season, they can be transported as intact nests (tubes, blocks, etc.) or as loose cocoons. As is characteristic of solitary bees, Osmia species are very docile and rarely sting when handled (only under distress such as when wet or squeezed); their sting is small and not painful, and their stinger is unbarbed. ==See also==