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ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER
Mission, Texas

Anthophora capistrata; digger bee; (c) Copyrght 2019 Paula Sharp

DIGGER BEES

Anthophora

DIGGER BEES
Genus Anthophora

 

Anthophora, commonly called digger bees, are entertaining, unusually noisy insects with a distinctive way of flying. They zip speedily around flowers and then stop abruptly, hovering in front of a blossom, sometimes angling their long tongues down a flower’s throat without letting their feet touch the petals.  Or they buzz raucously while clinging to the flowers, and thrust their faces so deeply into them that when the bees emerge, their heads and thoraxes are coated in pollen.

Anthophora are solitary – that is, each bee builds and provisions its own nest.  Nonetheless, digger bees are often gregarious, preferring to construct their nests close by one another, sometimes forming large aggregations that number in the hundreds or even thousands.  

As their name suggests, digger bees typically nest in the earth, either in level ground or vertical banks.  A few Anthophora species make tunnels in pithy stems and rotted wood, lining their nests with oils collected from plants. 

Female Anthophora construct ground nests by digging with their front legs and using their mandibles to loosen dirt.  In some species, such as Anthophora abrupta, females use their front legs to haul mud through the air; they then work the mud to moisten the dirt of dry nesting areas, softening it up for better digging. 

 

When expanding underground lairs, some Anthophora females pile excavated soil outside their holes in tall thin stacks called tumuli. Female Anthophora  vigorously defend their nests against predators. Anthophora females have been observed dragging parasitic bees bodily from nest holes.

Male digger bees, like the Anthophora californica shown here, may have thickly-built hind legs equipped with wide blades.  Such leg modifications are used for grasping female bees during mating. Male Anthophora often gather outside of nest tunnels dug by females.  The males sometimes pile together in scrums outside of nest entrances, awaiting the emergence of a female.  When she appears, they jump on her en masse.

Various species of Anthophora  have been documented engaging in boisterous behavior.  In 1929, the entomologist Phil Rau wrote of Anthophora abrupta: “They are neither timid nor aggressive, but …how conspicuous they are 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. They have none of the shy, stealthy ways of maneuvering, whereby some of the smaller and daintier varieties of bees and wasps hold their own in a competitive world.”

Entomologist Robbin Thorp recorded in 1969 that if one strolled through a nest colony of Anthophora  edwardsi,  "swinging an insect net about a meter above the ground, the females would aggregate in the plane of motion.  Thus it was possible to capture 25 to 50 females in five sweeps".  Thorp noted also that objects thrown over or onto the nesting site were likely to be followed aggressively by large numbers of females.  He found their  behavior to be remarkable, because solitary bees rarely act collectively in this manner.

Identification information: 

Anthophora are generally somewhat larger than honey bees and robustly built, with black or black-and-white-striped abdomens and beige or golden-brown thorax hairs.  Because of their hefty builds and black-and-pale coloration, digger bees are sometimes mistaken for bumblebees.  

Both male and female Anthophora possess exceptionally long tongues.  Females have shaggy hairs on their back legs, used to carry pollen. As noted, males, such as the California digger bee shown here, may have reddish or ornately-sculpted legs with sharp points and edges. 

 

Male digger bees of many species have pale masks on their faces, as shown in the photographs at right of Anthophora capistrata and Anthophora californica.  Male digger bees'  mandibles; their clypei and labrums (face parts above and between the mandibles); and their scapes (lower antennal segments) may be white, yellow or yellowish-white. Female bees tend to have black faces.  Typically, digger bees have “roman noses” or concave profiles.

Pollination

Female Anthophora practice buzz pollination -- that is, they vibrate their wing muscles, shaking pollen from the anthers of flowers.  These bees are exceptionally effective pollinators and play an important role in maintaining wildflower diversity, in part because their long tongues allow them to pollinate deep-throated and tubular blossoms inaccessible to many bees.

Digger bees are generalist pollinators that visit an impressively wide range of plants. Texas species feed on such flora as salvias; cacti and mesquite; verbenas; sunflowers, thistles, goldenrods, and other aster-family plants; melons and squash; roses; vetch; plants of the morning glory family; and evening primrose.

Anthophora californica - (c) Copyright 2019 Paula Sharp

A male California digger bee (Anthophora californica)

Anthophora californica digger bee leg - (c) Copyright 2018 Paula Sharp

Hind leg of a male California digger bee

Anthophora californica digger bee - (c) Copyright 2019 Paula Sharp

A female California digger bee drinking nectar from a flower

A male Anthophora capistrata digger bee - (c) Copyrght 2019 Paula Sharp

A male Anthophora capistrata

TAXONOMY OF ANTHOPHORA DIGGER  BEES

Order:   Hymenoptera

Family:   Apidae

Subfamily:  Anthophorinae
Tribe:  Anthophorini

Genus:   Anthophora

Species shown below:
  ​    Anthophora (Anthophoroides) californica 

            (California digger bee)

      Anthophora (Mystacanthophora) capistrata

            (Masked salvia digger bee)

Anthophora Species of the National Butterfly Center

Masked salvia digger bee

Anthophora capistrata
Family:  Apidae

Size:  12-13  mm  (male)

           14 mm (female)

Associated plant at NBC: 
Shrubby blue sage

(Salvia ballotiflora)

Plant family:   Lamiaceae

Golden dewdrops

(Duranta erecta)

Plant family:   Verbenaceae

When seen:
April & October 2019 

Anthophora capistrata; digger bee; (c) Copyrght 2019 Paula Sharp

A male Anthophora capistrata  

A male Anthophora capistrata digger bee - (c) Copyrght 2019 Paula Sharp

A male Anthophora capistrata  

Anthophora capistrata digger bee - (c) Copyright 2019 Paula Sharp

A female Anthophora capistrata

A note on Anthophora capistrata:  This species was first described by entomologist E.T. Cresson in 1878.  Capistrata means “wearing a headdress” or “wearing a halter,” a reference to the distinctive black-and-white pattern on the male bee's face.

 

Cresson painstakingly described this pattern, a trait that readily identifies the species.  He also noted other traits of the male Anthophora capistrata:  the male bee has black spots on the base of each mandible;  its scapes (bottom segments of the bee's antennae) are white; and the the bee’s head, thorax, first abdominal segment and legs are densely covered with hair.  The female Anthophora capistrata has a black face and lacks the ornate mask of the male bee.

Anthophora capistrata is found primarily in Mexico.  Within the United States, this species has been documented for the most part close to the Texas border.  Cresson based his description of Anthophora capistrata on an examination of two male bees found by Swedish entomologist Gustave W.  Belfrage during collecting expeditions he undertook in Texas in the mid-1880’s.  

Anthophora capistrata is associated with plants of the mint family (Lamiaceae).  The male bee shown here was observed energetically guarding a shrubby blue salvia bush in the third week of April, 2019.  The female bee was discovered in mid-October, feeding on shrubby blue salvia alongside several male bees.

California digger bee

Anthophora californica
Family:  Apidae

Size:  12 mm  (male & female)

Associated plants at NBC: 
 

Berlandier's Fiddlewood
(Citharexylum berlandieri)
Golden dewdrops

(Duranta erecta)
Plant family:  Verbenaceae

Shrubby blue sage

(Salvia ballotiflora)

Plant family:   Lamiaceae

Silver-leaf nightshade
(Solanum elaeagnifolium)
Plant family:  Solanaceae

Guayacan
(Guaiacum angustifolium)
Plant family:  Zygophyllaceae 

 

When seen:
Feb. - Nov.  2018-2020

California Digger Bee - Anthophora californica - (c) Copyright 2018 Paula Sharp

A male California digger bee  (Anthophora californica)

Anthophora californica digger bee - (c) Copyright 2018 Paula Sharp

A male California digger bee 

Anthophora californica digger bee - (c) Copyright 2019 Paula Sharp

A female California digger bee 

Anthophora californica digger bee female - (c) Copyright 2019 Paula Sharp

A female California digger bee 

CITE THIS PAGE:  Sharp, Paula and Ross Eatman.  "Anthophora."  Wild Bees of the National Butterfly Center of Mission, Texas. 15 Jan. 2019,  http://www.wildbeestexas.com.  Accessed [day/month/year guide accessed].

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