e efficiency. The stamen (the structure holding the anthers) of alfalfa flowers is held under tension by two flower petals, and springs forward with force when released by a visiting bee. This triggering discourages many bees, including honey bees, which learn to avoid being hit by the stamen by approaching the flower from behind, where they can gather nectar but not pollen. The alkali bee (Nomia melanderi), a native ground-nesting megachilid bee, is not discouraged by this unusual flower structure and is a major pollinator of alfalfa seed in some western states. It has been used as an effective pollinator of alfalfa when grown for seed in the western United States. In this case large areas of barren soil are provided for the nesting of this bee,
Mason Bees. These are a gentle beneficial insects that has potential as a pollinator of apples, cherries, and other tree fruits. It is found throughout most of North America, particularly in wooded areas but often around homes in towns and cities.
Mason Bees. Image Courtesy of Exzellente Bilder.
Homeowners sometimes become concerned when they see the bee entering cavities under shake siding or investigating nail holes or other cavities in wood during March through early June. These are not destructive insects, since they do not excavate holes in the wood, though they will clean out loose debris. No controls are recommended, since no damage is done. To prevent the bee from nesting, holes may be filled with caulking.
The females use existing holes in wood for a nest. They choose holes slightly larger than their body, usually 1/4 to 3/8 inches in diameter. The bees first place a mud plug at the bottom of the hole, then brings in 15 to 20 loads of nectar and pollen which they collects from spring flowers, including apples and other fruits. If you watch the bees closely as they enter the nest, you can see the pollen on the underside of the abdomen.
When the female has provided a sufficient supply of food for the larva, she lays an egg and then seals the cell with a thin mud p