Mason Bees are solitary nesting bees. They are usually quite calm and rarely sting. This mason bee is hanging onto a redbud flower. There are as many as 200 species of native bees that all get called mason bees. Mason bees can be very effective pollinators. They are quite active and can pollinate as many as 10 times as many flowers as a honey bee can. We have had a severe decline in the number of honeybees in our garden and an equivalent increase in the numbers of these guys and other native bees. In addition to collecting pollen they eat decaying plant material.
I have put out mason bee houses in the hopes of encouraging them. So far there is no evidence that they have been interested in my constructions, but they are regulars in my garden. Obviously the mason bees have found some local logs or fences to nest in. The recommended mason bee house construction calls for holes that are 5/16" in diameter, bored most, but not all of the way, through the wood. The holes should be spaced at least 3/4" apart. A roof is nice to keep the wood from getting wet and shading the house. They prefer a South East exposure. The houses can be painted but you should not use a wood preservative as that may harm the bees.
High resolution photos of the Mason Bees are part of our garden image collection.