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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

A bumble bee, or not a bumble bee, that is the question: Miner bees, Anthophora abrupta

 

More closely related to a carpenter bee than a bumble bee, the earth mining bee, Anthophora abrupta, is an important pollinator of many flowering trees, shrubs, and herbaceous plants.

 

Several years ago along one of my favorite trails, a majestic old tulip poplar tumbled over exposing an impressive vertical root plate about four feet in diameter. Over the years, the exposed matrix of earth and roots has become the perfect site for several species of ground nesting bees to take up residence. Early one steamy morning last week while passing the fallen giant I was distracted from my reverie by loud buzzing coming from the root plate. Amidst the soil and roots a swarm of boisterous bumble bee–like insects cavorted, digging holes in the soil and performing aerial acrobatics.

A pair of lady miner bees busily ready their earthen tunnels in preparation for provisioning them with nectar and pollen, and depositing eggs within.

In previous episodes we met bumble bees and learned a bit about their societies and way of life. However, these bees did not conform to the bumble bee stereotype of workers sharing a colony with sisters performing the bidding of their mother, the queen. Each of these gals was clearly a standalone, excavating its own gallery in the soil independent of the shenanigans of its neighbor. Fortunately, the wizard of native bees, Sam Droege, set me straight as to who these fascinating ladies really were. Miner bees and digger bees belong to a clan known as anthophorid bees, a curious group that includes carpenter bees we met in previous episodes. Due to their distinctive pattern of black and yellow hairs and loud buzzing demeanor they are often mistaken for bumble bees. But in the miner bee world, every lady is a queen, each creating her own gallery in the soil. Tunnels in the soil may be five or more inches long and are lined with brood cells.  After excavating these cells, female bees seal and waterproof each one with a glandular secretion.  Cells are then provisioned with pollen and nectar, eggs are deposited, each cell is sealed, and then the tunnel is plugged with clay. The babes inside consume the nutritious larder, develop over the course of the year and emerge the following spring as adults. These handsome bees are important generalist pollinators and their host list includes plants in twenty families ranging from American persimmon to Virginia bluebells. According to Graham et al. 2011 they are “potential pollinators of many important crops including: cranberry, tomato, blackberry, asparagus, persimmon, clover and raspberry.”

 

Amidst the clay and roots of a toppled tree, miner bees excavate galleries soon to be nurseries for their offspring. A close resemblance to bumble bees probably fools predators as well as folks unfamiliar with these interesting pollinators.

The Bee Wall at the University of Maryland  is a great place to see marvelous mining bees in action. Image: Lisa Kuder

As a final thought to this episode, while many folks have a fear of bees, which maybe well-founded for those with allergic reactions, Anthophora abrupta is a very docile citizen of the bee world. My cameras were within centimeters of these beauties as I recorded this episode. Meanwhile, a group of youngsters and their parents stopped by the well-travelled trail in Columbia, Maryland to witness and enjoy these bees along with me. To enjoy some of these interesting solitary bees, keep your eyes open for muddy riverbanks or clay-caked roots of fallen trees where miner bees like to construct their homes, or plan a trip to the Bee Habitat Wall sponsored by Bug of the Week at University of Maryland’s Arboretum Outreach Center.

References

We thank Sam Droege for assistance in identifying bees and for providing information on their habitats and biology. Featured Creature fact sheet “Miner bee, Anthophora abrupta “by  Jason R. Graham, Jamie Ellis, Glenn Hall, and Catherine Zettel Nalen of the University of Florida was used as a reference for this episode.