Leafcutter and Mason bees (Family: Megachilidae)
Many Megachilidae are solitary bees whose scopa, pollen-carrying structure, is on the bottom of their abdomen.
Leafcutter bees usually nest in existing holes such as hollow stems or cut off canes. These gentle bees get their name due to their habit of cutting out small round and elongated holes in plant's leaves. These holes don't normally damage the plant. Leafcutter bees line their found homes with pieces of leaves, overlapping them like they are rolling a cigar. Round pieces are used for the bottom of the tube while oval pieces line the sides of the nesting tube. Don't begrudge leafcutter bees their leaves though, one leafcutter bee can pollinate as well as 20 honeybees.
Unlike honeybees, leafcutter bees do not have pollen baskets on their hind legs. Instead they collect pollen on their abdomen or stomach. Queen bees gather pollen and nectar to provision their nest for the young. They add food to the bottom of their nest hole and lay one egg. That cell is sealed with a round leaf piece and they repeat the process. The larvae develop into adults and overwinter in their brood cells. Once spring appears the bees chew through their home to emerge to begin a new cycle.
Mason bees also like to nest in natural cavities, tubes, reeds or holes. Unlike most other bees, mason bees use mud or chewed plant debris to remodel their new house. After constructing a suitable and tubular abode, the queen bee packs the bottom of the nest with pollen and nectar. One egg is laid and it is sealed with mud. The female repeats this process until her nest cavity is filled with small 'cells' with eggs and food. Larvae hatch, eat the food and form a pupa. They hibernate in the cocoon state and hatch in spring.
Mason bees are very nonaggressive and don't sting unless squeezed or sat on. Due to their peaceful nature and great pollinating skill many people try to attract mason bees to their garden. You can easily buy or make mason bee houses out of wood, or recycled paper, or just about anything (here's a fun website with good videos and photos on how to make all sorts of mason bee houses) to attract these helpful native bees to your yard.