Leafcutter bees (Megachile species) are an important source of pollen and nectar in gardens. These small native bees measure about 1/4 inch long with a pollen brush on their abdomen.
Leafcutter bee females build nests in soil, rotting wood or the pithy center of plant stems. Their nests look like cigar-shaped cells and each contains a bee egg as well as nectar and pollen.
Contents
Pollen
Leafcutter bees collect pollen from many plants, as well as ornamental flowers such as roses and azaleas. They cut a half moon-shaped hole in the leaves of these plants for their nests without causing much harm to them.
These solitary bees don’t form colonies like honeybees, and will only sting if their lives are threatened. Their stings aren’t painful and far less irritating than a bee or wasp sting, however.
Female leafcutter bees search for tubular cavities to build brood cells lined with cutaway parts of plants. Inside these cavities she provides the cell with nectar and pollen, then lays an egg and seals it shut.
Female leafcutter bees construct tunnels out of plant material, similar to other solitary bees such as mason bees. They use hollow stems, decaying wood, empty tunnels left by beetles, wind chimes and even abandoned snail shells for this purpose.
Nectar
Leafcutter bees feed on nectar from flowers and other plants, as well as pollen.
Bees typically feed on nectar from flowers, but can also consume extra-floral nectaries found on green leaves and some fruits. This helps regulate their diet to a balance of water and sugars.
Contrary to honey bees, which live in colonies, leafcutter bees are solitary creatures and will only sting if they feel their lives are being threatened.
Adult female birds search for hollows to build nests, lined with cutaway plant parts or soil. Each cell is supplied with pollen, nectar and a small amount of water.
Once the nest is built, the female seals it with bits of plant leaves to protect her eggs from predators while she’s away. Depending on the species, leafcutter bees typically produce one to two generations per year.
Nests
Leafcutter bees build nests in a variety of places, such as soil, rotting wood or plant stems. These nests take the shape of cigars and contain multiple cells with stored pollen balls or loaves and eggs inside each cell.
Each cell is secured with another piece of leaf cut from the same plant. In this nest, the female bee provides food for her young by collecting nectar and pollen from flowers as she travels between plants.
In addition to gathering food for her young, leafcutter bees are important pollinators of wildflowers, fruits and vegetables. As they forage, their hairy abdomens carry pollen around with them as they navigate.
Like mason bees, leafcutter bees lay their eggs on stored pollen and then cover them with more leaves. The larvae hatch from these cells in summer and feed on stored food before pupating into adults in autumn. After spending wintering within their nest cells, adult bees emerge in spring to start pollinating again!
Nesting Tubes
Leafcutter bees often build nests in pre-made cavities, twigs and soft rotting wood. Once they find an appropriate cavity, females start collecting segments of leaves and overlapping them to form a series of cells in a cylindrical ‘cigar’ shape.
Leafcutter bees fill each cell with plant parts, such as leaves and petals, usually from roses, bird’s foot trefoil or other flowering plants.
Nest cells are filled with nectar and pollen, where an egg is laid and sealed within each cell. The young bees emerge the following season.
Like mason bees, leafcutter bees tunnel through soft, rotting wood. While less damaging to wooden buildings than carpenter ants, their tunnels may leave behind coarse sawdust at their entrances.
Leafcutter bee nesting trays are left intact over winter, unlike mason bee hives which break their trays apart to harvest cocoons in the fall.
