Pest Identification And Information

ANDRENID BEES

Life cycle.

Andrenid bees (or "digger bees" or "mining bees" as they are also referred to) are solitary ground nesters. They are important pollinators of wild blueberry both in number and pollination effectiveness. A week or so before wild blueberries bloom, both adult males and females emerge from nests constructed the previous season. After mating, the female excavates a burrow in the soil that consists of an entrance similar to that of an anthill, a vertical shaft and a series of lateral tunnels terminating in brood chambers (see Figure 1). These burrows may be as deep as 45 cm (18 inches). Within the burrow, the female applies a waterproof lining to the walls of the brood chamber, then lays an egg on a mass of pollen and nectar. This mass sustains the larva until the fall, when bees reach the overwintering adult stage. Early in the spring, the bees emerge from the ground to begin the cycle again. Digger bees often nest within wild blueberry fields, choosing sites that have sandy well drained soils and some protective cover by vegetation. The choice of suitable sites often means that several nests are dug relatively close to each other.

Although Andrenid bees are able to forage on a wide variety of plants, they tend to remain loyal to blueberry once they have begun to forage on it.

Figure 1: Examples of burrows built by andrenid bees and other similar bees

ANDRENID BEES AT A GLANCE:

• Actual size: 7-14 mm (¼ - ½ inch).

• Buzz pollinators.

• Flowers visited per minute: 5-10.

• Some of the other wild plants that are important to blueberry andrenids: shadbush, currants, raspberry and blackberry, maple, strawberry, willow, labrador tea, huckleberry, bunchberry, chokecherry, rhodora, dandelion, lambkill, rose, sumac, clovers and sweet clovers, hardhack, apple.

• Preferred habitat features: These bees prefer pliable soil with a thin organic layer on south-facing banks amidst a plant stand of sparse to intermediate density. These bees would definitely benefit from the presence of other plants which flower before and after the wild blueberry.