Bees in the Bombus genus, commonly called bumble bees, can be found throughout Michigan. They are, in general, large bees with body lengths that may exceed an inch, and they are hairy and black with yellow or orange markings. Female bees are somewhat larger than male bees.
More than a dozen species of bumble bee are established in Michigan, and the species can be differentiated from one another by the coloration of their bodies. The common eastern bumble bee, for example, has a yellow thorax and a yellow band at the front of its abdomen, but the back of its abdomen is entirely black. The half-black bumble bee has a yellow thorax with a black spot between its wings, and the yellow part of its abdomen is larger than that of the common eastern bumble bee.
Andrenid bees, commonly called mining bees or burrower bees, are smaller than bumble bees, with a body length between 1/4 and 3/4 inch. They are only moderately hairy, and they are typically dark brown or black, sometimes with yellow, white or reddish markings. The ends of their abdomens are flattened in comparison to bumble bees or other species such as honey bees.
Both bumble bees and mining bees nest in the ground. Bumble bees are social bees, and their nests are inhabited by a fertile queen, infertile female worker bees and male drones; the queen lays eggs and tends to them and the larvae once they hatch, and the other bees build the colony and forage in the garden for nectar. Mining bees, in contrast, are not social bees; each female builds a nest on her own, laying eggs in individual tunnels and sealing the tunnels after the eggs are laid. Groups of mining bees may build their nests close together, however, giving the appearance of an organized colony.
The larva of both bees are pale-colored, segmented grubs. In bumble bee colonies, the larvae are tended by adult bees, but in mining bee nests, the larvae are abandoned by the females and left to develop on their own.
Bumble bees often build their nests in abandoned animal burrows or bird nests, but mining bees dig their own tunnels, often leaving a small pile of dirt around the finger-diameter-sized entrance to the nest.
Benefits and Control
Both of these types of bees are capable of stinging, but neither bumble bees nor mining bees are especially aggressive, and they are unlikely to sting unless they are directly and obviously threatened. Both types of bees are very effective plant pollinators and are indispensable for the role they play in the ecology of the garden. Therefore, it's best to tolerate the presence of these bees and avoid areas where they're nesting.
Mining bees prefer to build their nests in bare ground or in areas where turf grass or other vegetative cover is thin, so to discourage the bees from nesting in parts of the garden or landscape frequented by people, do your best to maintain thick, healthy turf or ground cover in those areas.