
Digger Bees
Of the dozens of varieties of bees, digger bees are among the more interesting. Like honey bees and bumblebees, digger bees are members of the Apidae family; however, they are solitary rather than social bees. In this regard they have more in common with carpenter bees — yet another variety of the Apidae family. There are more than 750 distinct species of digger bees worldwide; all of these species are solitary. Digger bees are large — up to 3 centimeters in length. They are robust, fast flying, and hairy, their fur almost velvety, with visibly protruding faces. Their abdomens are often banded, the bands colored a metallic blue. When digger bees fly, their wings appear disproportionately short in comparison with their large bodies; because of these short wings, the buzzing sound they make when flying is more of a high-pitched whine. As their name suggests, digger bees build their nests in the ground, digging tunnels in the soil. They are fairly choosy about their nesting sites; the soil must display optimal slope, aspect, density, and drainage. Sandy, well-drained soils on south-facing banks are best, especially if there is some protective cover such as low-lying vegetation. Wild blueberry fields are a favorite of digger bees. Because such optimal sites can be hard to find, hundreds of digger bees, all operating individually, may construct their nests in close proximity to each other. These dense aggregations of individual nests give the appearance of a colony, and perhaps the bees find comfort being among others of their own kind. Nests are constructed by female digger bees, primarily for the purpose of laying eggs and raising young. A digger bee nest consists of a central shaft that extends from a few inches to as deep as 18 inches below the ground, with a series of individual dug-out cells protruding laterally from the shaft. One species of digger bee — the Pacific sand dune bee — digs nests in coastal sand dunes in California, Oregon, and Washington that can be nearly a meter deep. Other species will use the excavated soil to construct a characteristic turret above ground, marking the entrance to the nest as a sort of chimney-like extension of the entrance. If the soil is dry, the bee may forage for water, carrying water back to make excavation easier. The bee will line each individual cell with a wax-like, waterproof secretion. When the nest is complete, the bees will collect pollen and nectar from flowers; they bring these nutrient-rich food sources back to their nests and pack it into the cells. They will then lay their eggs in the nutrient-packed cells. Male digger bees, meanwhile, lead separate lives. They will hover around nesting areas, waiting for females to emerge from their nests so that they can mate. Sometimes males will dig their own small holes in the vicinity; often there is competition among male bees for prime locations, with the larger-sized males winning out. At night, male digger bees will sometimes congregate and rest in nearby shrubbery, or they will retire to their own nests. Mating occurs in the late spring and egg-laying in summer; the resulting bee larvae reside in their secure underground cells, nurtured by their mother, through the fall and winter. The larvae are sustained through this long period by the nectar and pollen collected by the mother bee throughout the earlier summer months. In the late spring, the newly adult bees will emerge from their nests, males and females, and begin the mating cycle again. Digger bees forage for nectar and pollen from among a wide variety of plants, including all kinds of berries, currants, maple, dandelion, rose, sumac, clover, and more. Some species of digger bees are particularly important in the pollination of wild blueberry, particularly if they are nesting in a blueberry field. Stepping into a blueberry field filled with loudly active digger bees may be intimidating at first, but these bees are very nonaggressive, and they won�t sting unless handled or trapped in clothing. And even their stings are milder than honey bee stings. As with most bees, males don�t sting at all. Digger bees in fact are at some risk in their nesting areas; several parasites, such as velvet ants and blister beetles, may try to invade their nests. If you encounter a collection of digger bee nests in an area where you don�t want them, the easiest way to get rid of them is to change the surface of the nesting area, for instance by adding mulch or by watering the ground. The bees will then move to another location. Control by insecticide is difficult, as each individual nest would need to be treated singly, and there may be hundreds of individual nests.
Digger Bees














