The Orchard Mason Bee, Blue Orchard Bee, Orchard Bee and Mason Bee are all common names for Osmia lignaria, a north American native pollinating bee that is a wonderfully effective pollinator of early spring crops like cherry, plum, prune, Asian pear, raspberry and blueberries. In fact they are such generalist feeders that they will very effectively pollinate just about any pollen bearing flower that blooms in the early spring. Studies done in netted orchards show that 250 female orchard mason bees can pollinate apples as effectively as 50,000 honey bees. They will work in cooler weather and more dampness than honeybees and they are absolutely non-aggressive. They seldom wander very far from home and are easy to raise. This makes them the perfect pollinator for home gardens and boutique orchards. Mason bees don't make honey. They make great apples and cherries.
Mason bees are classified as solitary gregarious bees. This means that they have no real social interaction in the sense that a honeybee population would but mason bees do like to nest near each other. I like to refer to this as the New York Condo Consciousness. They are very happy all nesting in a huge colony but they don't actually talk to their neighbors. What does this mean for you? It means that mason bees don't protect their eggs after they lay them. They actually don't care about you or your children at all so they are the perfect backyard bee. The male has no stinger. The female has one but uses it so seldom that there is a common belief that mason bees can't sting. The females can but rarely do unless they are in a real bind. I have been stung when I slapped one on my arm once and was stung another time when I was opening a cocoon to show the bees to a customer. For some reason the female in the cocoon was perturbed that I interrupted her hibernation by cutting open the cocoon and pulling her out. Go Figure.
The life cycle of these bees is pretty simple. Every spring when the day time temperatures start to get over 50 degrees with some regularity and enough days have passed since the egg was laid the previous spring, the mason bees chew through their protective cocoons, through the mud walls that protect their nesting chambers, and emerge into your garden. The actual date varies across the country from mid February in warm winter areas to late May in colder climates and higher elevations. Remember it is day time highs that activate these bees. Night time lows and frost dates are not what we are tracking here. The males emerge first, anywhere from a few days to a few weeks before the females. They spend their time foraging for nectar to build up their strength and hanging around the nesting tubes waiting for the females to emerge. These males do a bit of incidental pollinating while feeding but the vast majority of the work will be done later by the female. The males are not gentlemen. They are more like randy teenagers so as soon as the females emerge from the nesting holes, the males mate with them and then go looking for another conquest. When all of the females have been mated the males die and the rest of the season is an all girl show.
Female mason bees spend their days gathering pollen and nectar from flowers within about 100 yards of their nests. They use this pollen/nectar mix to make a lump of bee bread and place it in the back of a found hole. When the proper amount of food has been place in the chamber the female backs in and lays a single egg into the food mass. They then build a mud door in the hole to create a small cell. They then place another lump of pollen and nectar against the outside of the mud wall, lay another egg into the new lump and create another mud wall to form another cell. They work their way down the length of the hole making cell after cell until they have filled the entire tube. Finally an extra thick masonry plug is constructed at the hole opening and the bee flies off looking for another hole. Female eggs are laid toward the back of the hole where it is nice and safe from marauders and male eggs are put toward the front of the holes. In this way a hungry invader is likely to eat males only and leave the girls safe and sound. In the mason bee world it is all about protecting the females. Only a few males need to survive to mate the next spring but every girl is important.
By early summer, all the adult females have laid their eggs and they die from what must be sheer exhaustion. The eggs spend the summer developing into new bees and by fall they are fully mature bees in newly spun cocoons still in the same nesting tubes. They then hibernate all winter and wait for the signs of spring that will have them emerge in your garden the following spring. In other words, every year you will see the children of the bees you had the previous year. The colony should continue to grow every year as long as they have holes to lay their eggs into and pollen with which to provision the egg chambers.