acters used to define this group are subtle, but they are nonetheless fairly recognizable; they are generally large (up to 3 cm), very robust, hairy bees, with visibly protruding faces, and the apical portion of the wings are studded with microscopic papillae. The abdomen is often banded, and in many Old World species of Amegilla these bands are metallic blue. The wings often appear disproportionately short compared to other bees, and their "buzz" is often a high-pitched whine, as they hover and feed on flowers. Males commonly have pale white or yellow facial markings, and/or peculiarly modified leg armature and hairs.
Attracting Digger Bees. Some digger bees nest in cracks or cavities in soft sandstone and dry exposed soil embankments. Some of these species will excavate tunnels in cliff sides by wetting the hard soil surface with water or nectar to soften it.
To attract these species, adobe bricks can serve as the equivalent of a wooden nest block. Such bricks can sometimes be purchased, in which case you can increase their attractiveness to bees by drilling nesting holes following the size recommendations listed above for wood blocks.
Adobe blocks can also be easily made where clay soils are common. To create one, half-fill a large bucket with clay soil, and then fill the bucket with water. Stir the mixture together to create muddy slurry and allow it to settle. Remove any sticks or debris floating on the surface and slowly pour off most of the water. Finally, pour the remaining sediment into a mold (such as a wooden box or small Styrofoam cooler), and allow it to dry for several days or weeks. Before it completely dries, you can make several 1-inch indentations, using the diameter guidelines above, to make it more attractive to bees.
Mount the brick, either singularly or in a stack. Adobe will not hold up well in wet climates and many need sheltering from rain. You might want to supply a shallow water source near your bricks to help bees excavate their nests.
Halictidae-Halictid Bees. This is a cosmopolitan family of the order Hymenoptera consisting of small (> 4 mm) to midsize (> 8 mm) bees which are usually dark-colored and often metallic in appearance. Several species are all or partly green and a few are red (Figure 49); a number of them have yellow markings, especially the males, which commonly possess yellow faces, a pattern widespread among the various families of bees. They are commonly referred to as sweat bees (especially the smaller species), as they are often attracted to perspiration; when pinched, females can give a minor sting.
Common Sweat Bee. Image Courtesy of Jon Sullivan
Most halictids nest in the ground, though a few nest in wood. They mass-provision their young by providing a mass of pollen and nectar formed inside a waterproof cell. Once an egg is deposited on this mass the cell is sealed off. Thus the larva is with all the food at one time that it needs for full development, as opposed to "progressive provisioning", where a larva is fed repeatedly as it grows, as in honey bees. All adult species are pollen feeders and may be important pollinators. Several genera and species of halictids are cleptoparasites of other bees (mostly other halictids). The most well-known and common are species in the genus Sphecodes, where the female enters the cell with the provision mass, eats the host egg, and lays an egg of her own in its place.
Halictidae are one of the four bee families that contain some species that are crepuscular. These bees are active only at dusk or in the early evening or sometimes truly nocturnal. In these cases they have greatly enlarged ocelli or simple eyes to enhance their night vision.
Megachilidae-Leaf Cutting Bees and Mason Bees. The Megachilidae are a cosmopolitan family of solitary bees (Figure 50) whose pollen-carrying structure (called a scopa) is restricted to the ventral surface of the abdomen (rather than mostly or exclusively on the hind legs as in other bee families).
Leaf Cutting Bee with Pollen Trapped on Underside of Abdomen.
Megachilid genera are most commonly known 