Updated: Mar 5, 2021
One of the Decatur area's earliest spring pollinators is the Mason Bee (genus Osmia). Mason Bees are a gentle, solitary bee. Unlike honey bees, they do not live in large colonies with a queen and thousands of worker bees. There are about 140 species of mason bees in North America. Georgia is home to some 19 native and introduced species of mason bees.
Tolerant of cool early spring temperatures, adult Mason Bees only live for four to six weeks. During that time, they are very busy raising the next generation of bees.
In late winter / early spring, adult female mason bees emerge, mate and begin looking for suitable holes in which to nest. Unlike Carpenter Bees, Mason Bees are incapable of boring their own holes. Instead, they seek out existing cracks and crevices, dried hollow plant stems, or woodpecker holes left in trees. They will also use holes left behind by nails in brick masonry or wood siding, and will gladly move into artificial nesting boxes.
Inside the hole, the female will -- like a mason -- construct a series of mud chambers, hence their name. Our red Georgia clay is a perfect building material for them. To encourage Mason Bees in your yard be sure to leave patches of bare, moist dirt available.
The female Mason Bee will then supply each chamber with a pile of nectar and pollen she collects, and lay a single egg in each. Sealing up the chambers with mud as she goes, the female mason bee will work her way from back to front, until she reaches the opening of the hole. She will seal the opening and then seek out another hole to begin the provisioning/egg laying process again.
Inside the chambers, the eggs will become larvae, which eat the stored food and grow until they are ready to spin a cocoon. During the pupal stage, the larvae will change into adult bees and stay in their cocoons until the following spring. Then, the adult mason bees will emerge when daily temperatures start to warm. They chew through their cocoons and push their way through the mud at front of the hole. Male Mason Bees, laid at the front of the hole, emerge first. They’ll mate with female bees as they emerge. The females will then look for holes in which to lay eggs and the year-long life cycle repeats!
As adults, Mason Bees are outstandingly efficient pollinators. They are widely used commercially alongside honey bees for pollination of early blooming fruit trees like apples.
Mason Bees produce only a single generation per year. A typical female will produce 30 offspring. Not all will survive. Some will fall victim to parasitic wasps which prey on Mason Bees during their vulnerable pupal stage.
For a Mason Bee-friendly yard:
Avoid using insecticides and herbicides -- mosquito spraying kills bees!
Leave patches of moist bare earth where mason bees can obtain mud
Leave snags or fallen logs
Plant native, perennial plants that bloom across a range of seasons, from early spring through fall
Provide a water source