If you’re lucky, you might come across a village of fast-moving summer bees that may look a lot like bumblebees at first glance but they may, in fact, be the big digger bee Anthophora abrupta. These black and yellow bees can be found going in and out of chimney-like holes found in patches of exposed ground. Their nests look like small, mud chimneys, and are generally built close to other individuals of their species. Solitary bees that nest in close proximity to others are known as “gregarious” species. Anthophora abrupta is a species with no common name and is known for its docile nature and is most likely incapable of stinging humans.
Taxonomy. Anthophora abrupta is in the family Apidae, subfamily Apinae, and tribe Anthophorini which also includes the genus Habropoda. The genus Anthophora is closely related to the genus Habropoda. Species in these genera may be hard to tell apart but they can be distinguished by the vein patterns on their wings. Unlike female bumble bees that collect pollen on their corbiculae—flat surfaces on the hind legs—Anthophora collect pollen on their scopal hairs located in their hind legs (see photo).
Where can you find it? Anthophora abrupta is widely distributed in the eastern United States as it can be found from east Texas to Florida, and north through southeastern Canada.
Life History. Like many solitary species, A. abrupta have no generational overlap. This means that the mother’s life will end in the season before her offspring emerge. Newly-hatched adult A. abrupta emerge from their nest sometime between April and June. Males generally emerge about five days prior to the females and begin looking for mates right after emergence. Females tend to sit near the emergence site, turning their heads back and forth to observe the landscape before they begin finding a nesting site. They mate shortly after emerging from the nest and within two days begin tunneling. Some of the females will reuse tunnels constructed in prior years by other females. Others may spend several hours hunting for a good nesting spot, tending to favor bare ground with small cracks or openings. Exposed banks are a common habitat for this bee.
When the construction of the underground tunnels begins, females use regurgitated water to soften the soil and will eventually dig about 5 inches. As she digs, the bee will remove beads of clay that she will then use to construct the exterior entrance of the nest that looks like a tunnel (see photo). The exact purpose of these external tunnels is uncertain, but they may protect the nest from parasitoids and rain, and also help keep the nests warm. Each nest typically houses about 8 cells behind an enlarged entrance chamber. While each female is on her own for nest-building, she may share a single entrance with another female.
At the end of the underground tunnels, the female creates individual cup-shaped cells lined with clay particles and coated with abdominal fluids that harden and waterproof the surface. Each cell houses an egg or larva with a pollen provision (mixture of pollen and nectar). The abdominal triglyceride-rich fluid produced by the females also serves as a source of nutrition for developing larvae. The larvae go through a number of developmental life stages (from larva to pupa) within about three weeks, and then overwinter as adults.
Plant use. Anthophora abrupta visits a wide variety of flowers and are considered generalist in their pollen preferences. They have been observed visiting flowers of Rhododendron, Oenothera, Penstemon, Rubus, Asclepias, Cornus, Delphinium, Iris, Monarda, Nepeta, Rosa, Diospyros, Melilotus, Trifolium, and Pastinaca species. Females are known to forage primarily in the morning as they perform nest-building activities in the afternoons.
Natural Enemies. A variety of parasites have been reported in the nests of A. abrupta, most notably chalcid wasps of the genus Monodontomerus. In addition, several species of flies can also occupy A. abrupta larvae cells and consume either the egg or the larva, and the pollen provision the female collected for her offspring. Anthophora nests can also be damaged by birds, lizards, and squirrels.
Relationship with Humans. Bees of A. abrupta are not easily disturbed by human activities. Even though the bees have a stinger, they generally only deliver a little pinching bite if handled roughly.
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Discover Life, https://www.discoverlife.org/20/q?search=Anthophora+abrupta
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US Forest Service, USDA: https://www.fs.usda.gov/wildflowers/pollinators/pollinator-of-the-month/anthophora-abrupta.shtml