Miner Bees Moving In
"...conspicuous as they noisily swing their ponderous bodies to and fro on the wing, arrive home and scramble into their burrows or come tumbling out headlong and dash off into the sunny fields, with all the exuberance of boys just out of school." Phil Rau, The Biology and Behavior of Mining Bees, Anthophora Abrupta and Entechnia Taurea, 1929
Students who ponder around the Reiley Garden or walk by the Arboretum Outreach Center on their way to class have noticed an interesting cob structure standing between a small pollinator garden and the Reiley Garden, with some new neighbors living in the wall. The pollinator garden is planted out with a long list of pollinator-friendly plants: New England aster, butterfly milkweed, black-eyed Susan, swamp milkweed, Joe-pye weed, rough leaved goldenrod, wild bergamot, yellow sneezeweed, blue hyssop, Cherokee sedge, Appalachian mountain mint, New Jersey tea, blazing star, obedient plant, little bluestem, grass-leaved goldenrod, prairie dropseed, foxglove beardtongue, culver’s root, spotted bee balm, gray goldenrod, Virginiana spiderwort, and pale purple coneflower. A vast variety of plants were used to create year round interest for the bees and provide ample pollen and nectar sources necessary for the survival of the bees occupying the pollinator habitat. This structure serves as a bee habitat, almost like a bee hotel. The structure is made from a mixture of clay and sand, referred to as cob. Straw is added to the cob to give it tensile strength. A miniature green roof planted with various sedums, bee balm, bee balm petite, catnip, creeping Jacob's ladder, wild bergamot, and mountain mint protects the cob structure from erosion and excessive water. But this is not the only cob/adobe habitat on campus. Take a walk to the Community Learning Garden, located between Eppley Recreation Center and the School of Public Health, then follow the gravel path along the rain garden and terraces to the bottom of the hill. You will see Styrofoam cubes containing cob/adobe stacked against one of the walls of Eppley. If you are patient, you may see several bees popping in and out of the structure.
Commonly referred to as miner bees or chimney bees, Anthophora abrupta are a solitary and gregarious ground nesting bee species. This bee species does not have overlapping generations and each female only cares for her own nest and offspring. Anthophora abrupta are a docile species and usually do not sting. They do not exhibit aggression or defensive behaviors regarding their nests but will bite if roughly handled. A. abrupta’s distribution spans from Texas to Florida and up the east coast into Canada. Miner bees are starkly different from honeybees. Honeybees are social, so they live together in nests or hives and they have a queen while miner bees are solitary and do not have a queen. Honeybees pollinate just like miner bees do, but honeybees make honey and beeswax while miner bees do not make honey. A honeybee’s life cycle is also different from a miner bee; a honeybee hatches in 6 days, will begin the pupa stage at day 15 and will be tended to and fed by worker bees, and will emerge as an adult 21 days after being oviposited as an egg. Later, you will read about the life cycle of miner bees and that the females provide everything the larvae will need within their cell. Honeybees are golden brown in color with black stripes on their abdomen and female honeybees have pollen baskets on their hind legs. Honeybees will sting if they feel it necessary, but can sting only once because as their stinger detaches it pulls their digestive tract out with it.
At a glance, A. abrupta can be mistaken for a bumble bee because brown-black hairs cover its head, legs, and abdomen, dense, pale yellow-orange hairs cover its thorax, and their nearly translucent wings have brown-black veins. Female miner bee adults range from 14.5-17 mm in length and their clypeus, the area between their eyes and mouth, strongly protrudes. Male miner bee adults range from 12-17 mm in length and are called “the mustached mud bee” because of their distinctive hairs on their yellow clypeus (University of Florida). This mustache actually carries pheromones used to attract females.
Adults emerge early April through late June but emergence is heavily influenced by climate and region. Males emerge five days prior to females. Anthophora abrupta mate on flowers and while females appear to mate with one male, a single male will mate with several females. After a female has mated, she begins looking for a nesting site, often returning to her place of emergence. Females that emerge early in spring will zigzag through the air inspecting places to begin excavating their nests. Females that emerged late in the season will nest in clumps in close proximity to the early emerging females. Females dig tunnels roughly 11 cm long, most oftentimes in clay. Water is required to soften the clay or adobe the female wants to burrow into; this is why their nests are usually found in close proximity to rivers or streams. After 6 hours the female completes the 8 cm long turret, which resembles a chimney, at the opening of her nest. Several ideas have been proposed to explain the purpose of the turrets including they provide protection from debris, parasites, and rain, aid in nest recognition, encourage other females to nest nearby, or serve as a bee HVAC system or solar heaters. A female will dig out about 7 urn- shaped cells in her burrow, line each with secretions from her Dufour gland, mix together pollen, nectar, and Dufour secretions to create a pad to oviposite an egg onto, and then caps the cell. The eggs resemble bent, white rice and hatch after 5 days. The pollen, nectar, and Dufour secretations mix and the cell lining serve as food for the larvae as they go through 4 instar stages in 3 weeks. Without molting, the fourth instar will prepupate before overwintering for 9.5 months. When spring arrives, they shed the prepupal skin and take 2.5 weeks to darken before emerging as adults and begin the cycle over again.
For more information about the pollinator habitat located in the Reiley Garden, follow this link to one of our earlier articles https://arboretum.umd.edu/solitary-bee-wall-pollinator-garden.
For more information on the bee wall project, including the purpose of the wall, who funded it, the inspiration, etc., please visit: http://umdarboretumandbotanicalgarden.blogspot.com/2015/09/wild-pollinators-move-into-their-new.html
Information for this article was sourced from the following:
The University of Florida’s Entomology Department’s Featured Creatures website http://entnemdept.ufl.edu/creatures/misc/bees/anthophora_abrupta.htm.
Graham, Jason R., Willcox, Everett, and Ellis, James D. The Potential Management of a Ground-Nesting, Solitary Bee: Anthophora abrupta (Hymenoptera: Apidae). Florida Entomologist, 98(2):528-535. http://www.bioone.org/doi/pdf/10.1653/024.098.0220.
Discover Life’s website http://www.discoverlife.org/20/q?search=Anthophora+abrupta.
Encyclopaedia Britannica’s website https://www.britannica.com/animal/honeybee.
Oder, Tom. How to Identify Different Types of Bees. 26 July 2017. https://www.mnn.com/your-home/organic-farming-gardening/stories/how-identify-different-types-bees.
The Honeybee Conservancy website https://thehoneybeeconservancy.org/2017/06/22/honey-bees-heroes-planet/.
Written by Lydia Printz