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ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER

Mission, Texas

Exomalopsis mellipes; Copyright 2023 Paula Sharp

ANTHOPHORULA  &  EXOMALOPSIS

Exomalopsis Species of the National Butterfly Center

THE BEE TRIBE EXOMOLOPSINI

Genus Anthophorula

Genus Exomolopsis

If you live in more northern parts of the United States, you may never have had the pleasure of encountering an Exomalopsis.  These are beautiful bees. They are uniquely colorful:  their legs may be rust-orange or multi-colored, and their eyes are brilliant green or blue-gray. Their abdomens are dark and ringed with pale hairs.  Females have luxuriant scopal hairs on their hind legs evocative of the groomed fur of champion show dogs.  Males tend to have very long antennae, and  partly-yellow jaws.  Exomalopsis are frequent visitors to the National Butterfly Center during the spring and fall.

These bees deserve a name that reflects their elegant beauty.  Nonetheless, they instead bear the hefty label “Exomalopsis”.  In Greek,  Exomalopsis literally means “not bad-looking”.   (Exo= without; mal=bad; opsis=appearance).  Thus, loosely translated, one might call the Exomalopsis the "not-so-ugly bee".  

Anthophorula is a close cousin of Exomalopsis:  together, these two genera comprise the bee tribe Exomalopsini.   Anthophorula is a genus of hairy bees that often have dark abdomens banded with pale hairs.  Like female Exomalopsis, female Anthophorula have lush scopal hairs on their back legs.  Males sport long antennae and often have yellow facial markings. 

 

Anthophorula tend to run smaller than most Exomalopsis.  (In Greek, the name Anthophorula means "little flower bearer".)  Anthophorula tend to appear at the National Butterfly Center in early April, shortly before prickly pear cactus blooms in Hidalgo and Starr Counties.

Anthophorula vs. Exomalopsis

 

Exomalopsis and Anthophorula share a trait that the legendary entomologist, Charles D. Michener, noted was common to all members of the tribe Exomalopsini:  they have a long row of erect, well-separated hairs lining the inner side of each compound eye orbit.   

Other minute differences, shown in the accompanying photo strip, separate these two genera.  According to Michener:  (1) The clypeus (the face part above the jaws) of the male Exomalopsis is always dark. The Anthophorula  male’s clypeus, however, may be yellow.  (2) The hind knee plates are larger on Exomalopsis males than on Anthophorula males. (2) The stigma of the forewing is proportionately larger in Exomalopsis; in Anthophorula, the stigma is less than half the length of the marginal cell, with some exceptions. (A few species of Anthophorula also have two marginal cells instead of three.)  

Exomalopsis and Anthophorula behavior

 

Both Exomalopsis and Anthophorula are solitary and nest in the ground.  In both genera, each female bee provisions her own individual nest, digging out oval egg chambers and coating them with a thin waterproof lining.  Females store pollen for offspring on a “foot,” a small mound of dirt slightly elevated from the nest floor, to protect against moisture.  

Despite their solitary status, Exomalopsis and Anthophorula may live communally, with several females inhabiting a single burrow that shares a common entrance.  Within at least one Exomalopsis species, E. solani, females even aid one another in storing pollen.  Such behavior is relatively rare among bees. 

Pollinator plants

 

Many Exomalopsis are pollinator generalists. At the NBC, Exomalopsis are frequent visitors to an array of wild and garden flowers, most notably crucita, croton, mallows and small-flowered Asteraceae.

Anthophorula are also often generalist pollinators; some, however, specialize in pollinating such plants as gumweed and leafy spurge, while others exhibit a preference for plants in the aster and buckwheat families.  The  Anthophorula compactula shown below has appeared nearly exclusively on prickly pear cactus, twisted rib cactus and red prickly poppy at the National Butterfly Center and abutting  areas.  Nonetheless, this species is known to visit a broad spectrum of plants.  

Some Exomalopsis and Anthophorula are capable of vibratile ("buzz") pollination and are thus good pollinators of crops in the tomato family (Solanaceae).  Plants in this family, which includes peppers, eggplants and potatoes, require this special pollination method (in which the bee vibrates its wing muscles to shake pollen loose from a flower's anthers). This capability is an important trait, because honey bees cannot buzz pollinate and thus cannot be relied on to pollinate such crops.  At the National Butterfly Center, Exomalopsis can be observed visiting the wildflower silver-leaf nightshade, a member of the Solonaceae family. 

Species range and Identification information: 

Both Exomalopsis and Anthophorula are found only in the Western Hemisphere. Ten species of  Exomalopsis inhabit the United States.  At least 7  have been documented previously in Texas:  Exomalopsis analis, E. birkmanni, E. mellipes,  E. snowi, E. solani, E. solidagnis and E. tibialis.  All but the last of these appear in the Valley.

Little photographic documentation of Exomalopsis and Anthophorula species is widely available, and thus identifying them can be challenging for naturalists and pollinator enthusiasts. The Exomalopsis and Anthophorula species shown here were identified through the aid of Texas bee expert John L. Neff, President of the Central Texas Melittological Institute.  Explanations of distinguishing traits of individual  Exomalopsis and Anthophorula species found at the NBC are given below, together with detailed photographs.

Anthophorula compactula bee - (c) Copyright 2019 Paula Sharp

A male Anthophorula

Exomalopsis mellipes - (c) Copyright 2018 Paula Sharp

A female Exomalopsis, showing the bushy scopal hairs typical of the genus

ANTHOPHORULA  vs. EXOMALOPSIS

Exomalopsis hind leg & scopal hairs - (c) Copyright 2018 Paula Shap

Leg of a female Exomalopsis

TAXONOMY OF EXOMALOPSINE BEES

Order:   Hymenoptera

Family:   Apidae
Subfamily:  Eucerinae

Tribe:  Exomalopsini

Genus:   Exomalopsis

Species shown below:

     Anthophorula (Anthophorula) compactula

          (Compact Anthophorula)

     Anthophorula (Anthophorula) completa

          (Complete Anthophorula)

     Exomalopsis (Exomalopsis) analis
          (Ringed Exomalopsis)

     Exomalopsis (Exomalopsis) mellipes
           (Honey-footed Exomalopsis)

     Exomalopsis (Exomalopsis) similis
          
 (Similar Exomalopsis)
     Exomalopsis (Phanomalopsis) snowi
         
 (Snow's Exomalopsis)

     Exomalopsis (Stilbomalopsis) birkmanni
          
Birkmann's Exomalopsis)
     Exomalopsis (Stilbomalopsis) solani 
          
(Solanum Exomalopsis)

Anthophorula Species of the Lower Rio Grande Valley

Compact anthophorula

Anthophorula (Anthophorula) compactula


Family:  Apidae

Size:  4.5 mm-5.5 (male)
        
 6-7 mm (female)

Associated plants
Prickly Pear Cactus

(Opuntia engelmannii)
Twisted-rib cactus
(Thelocactus setispinus)

Plant family:  Cactaceae

Red Prickly Poppy

Argemone sanguinea

Plant family: Papaveraceae

When seen:  
April - June

NBC (Hidalgo Co.)

Dos Venados Ranch
Rio Grande City, TX (Starr Co.)

Anthophorula compactula bee - (c) Copyright 2019 Paula Sharp

A male Anthophorula compactula

Anthophorula compactula bee - (c) Copyright 2019 Paula Sharp

A female Anthophorula compactula

Anthophorula compactula bee - (c) Copyright 2019 Paula Sharp

A male Anthophorula compactula on the head of a dime

In the Lower Rio Grande Valley, this beautiful small bee emerges in spring.  Male Anthophorula compactula appear in early April in Hidalgo and Starr Counties, feeding on Texas prickly pear cactus.  Female bees surface about ten days after males.  They usually are found collecting pollen from three different plants -- red prickly poppies, Texas prickly pear and twisted rib cactus.

An important distinguishing characteristic of this species is a minute trait relating to the bee's wings:  each forewing of the male and female  Anthophorurla compactula has only two submarginal cells.   This trait aids in distinguishing this species from the similar Anthophorula completa  shown below. Other notable traits that help in identifying Anthophorula compactula include:  (1) male bees have extensive yellow masks on their lower faces;  (2) male bees' antennae are striped black-and-yellow on their hind surfaces; (3) female bees have black scopal hairs, sometimes commingled with reddish -brown hairs,  on their lower  hind legs.

Complete anthophorula

Anthophorula (Anthophorula) completa


Family:  Apidae

Size:  4.5-5.5  mm (male)

          6-6.5 mm (female)

Associated plants:
Silver bladderpod

(Physaria argyraea)

Plant family:  Brassicaceae


Wrinkled globemallow
(Sphaeralcea hastulata)

Plant family:  Malvaceae

When and where seen:

April 17, 2023

Dos Venadas Ranch
Rio Grande City, TX  (Starr Co.)

Anthophora completa; Copyright Paula Sharp 2023

A male Anthophorula completa

Anthophorula completa (female); Copyright 2023 Paula Sharp

A female Anthophorula completa

Anthophorula completa originally was considered a variation of Anthophorula compactula:  to the naked eye, females appear nearly identical.  Nonetheless, Anthophorula compactula and A. completa can be differentiated easily by examination of their wings under magnification:  the forewings of Anthophorula compactula have two submarginal cells, while those of A. completa have three. The wings of both are glassy with brown veins;  those of Anthophorula compactula darken toward the tips. 

 

Males of the two species also differ in other ways:  the antennal scapes of male Anthophorula compactula are a mottled black-and-yellow, while those of A. completa are predominantly black.  In addition, on Anthophora compactula, the rear surface of the flagellum is yellow with black stripes.  On Anthophorula completa, the dark areas of the flagellum are large, nearly filling the back surface of each segment. The black areas of the antennae of the male Antophorula completa bell outward, giving the antennae a scalloped look, and the flagella themselves are curved.

Female Anthophorula compactula and Anthophorula completa show only subtle differences from each other, even under magnification (apart from the variation in forewing submarginal cells).  On female Anthophorula compactula, the hair on the scutum (front section of the thorax) is mosslike and light-colored; on A. completa, the hair on the scutum is longer and brownish.  On Anthophorula completa, the inner hind-leg scopal hairs are dusky and black; on A. compactula. they may be reddish.  The female Anthophora compactula may be as large as 7 mm, while the female A. completa tends to run smaller.

Anthophorula completa and Anthophorula compactula have a similar range -- both are found predominantly in the western and southwestern United States.  In the Valley, Anthophorula compactula is commonly associated with cacti. Anthophorula completa is more likely to be found on mallows. 

Food plants at NBC:  

Crucita

(Chromolaena odorata)

Skeleton-leaf goldeneye

(Viguiera stenoloba)

Seaside goldenrod

(Solidago sempervirens)

Plant family:  Asteraceae

Low croton 

(Croton humilis)

Plant family:  Euphorbiaceae

Texas ebony
(Ebenopsis ebano)
Plant family:  Fabaceae

When found: 
June, November

Snow's Exomalopsis

Exomalopsis (Exomalopsis) snowi

 

Family:  Apidae

Size:  8 mm  (female); 7 mm (male)

Exomalopsis snowi - (c) Copyright 2018 Paula Sharp

A female Exomalopsis snowi

Exomalopsis snowi - (c) Copyright 2018 Paula Sharp

A male Exomalopsis snowi

Honey-footed Exomalopsis

Exomalopsis (Exomalopsis) mellipes

Family:  Apidae

Size:  10 mm  (female)
           8-9 mm (male)

Food plants at NBC:  

Crucita

(Chromolaena odorata)

Seaside goldenrod

(Solidago sempervirens)

Romerillo

(Bidens alba)

Plant family:  Asteraceae

Prickly Malvastrum

(Malvastrum coromandelianum)

Plant Family:  Malvaceae

Cenizo 

(Leucophyllum frutescens)

Plant family:  Scrophulariaceae

Whitebrush

(Aloysia-gratissima)

Plant Family:  Verbenaceae

When found: 
June-July, September - November

Exomalopsi mellipes - bee - (c) Copyright 2018 Paula Sharp

A female Exomalopsis mellipes

Exmalopsis mellipes - (c) Copyright 2019 Paula Sharp

A female Exomalopsis mellipes

Exomalopsis mellipes (male), Copyright 2019 Paula Sharp

A male Exomalopsis mellipes

Ringed Exomalopsis

Exomalopsis analis

Family:  Apidae

Size:  8-9  mm  (female)

Food plants at NBC:  

Crucita

Chromolaena odorata

(Family  Asteraceae)

Whitebrush

(Aloysia-gratissima)

Plant Family:  Verbenaceae

June, November

Exomalopsis analis - (c) Copyright 2018 Paula Sharp

A female Exomalopsis analis on crucita

Exomalopsis analis  - (c) Copyright 2018 Paula Sharp

A female Exomalopsis analis from above

Similar Exomalopsis

Exomalopsis similis

Family:  Apidae

Size:  6-7 mm  (female),  4-5 mm (male)

Food plants at NBC:  

Resinbush

Viguiera stenoloba

Seaside goldenrod

(Solidago sempervirens)

Romerillo

(Bidens alba)
(Family Asteraceae)

Silver-leafed nightshade
Solanum elaeagnifolium
(Family Solanaceae)

When found:

June-July, Sept. - Nov.

Exomalopsis similis; (c) Copyright 2018 Paula Sharp

A female Exomalopsis similis

Exomalopsis similis (female) - (c) Copyright 2018 Paula Sharp

A female Exomalopsis similis on the head of a dime:  this is a small bee.

Exomalopsis similis bee - (c) Copyright 2019 Paula Sharp

A male Exomalopsis similis 

Solanum Exomalopsis

Exomalopsis solani

 

Family:  Apidae

Size:  10 mm  (female)

Associated plant at NBC:  

Shrubby blue salvia

(Salvia ballotiflora)
Family: Laminaceae

Silverleaf nightshade

Solanum elaeagnifolium
(Family Solanaceae)

When seen:  October-November

Exomalopsis solani bee - (c) Copyright 2019 Paula Sharp

Female Exomalopsis solani

Exomalopsis solani - (c) Copyright 2019 Paula Sharp

Female Exomalopsis solani

Birkmann's  Exomalopsis

Exomalopssis birkmanni

Family:  Apidae

Size:  11 mm  (female)

Associated plant at NBC:  

Cenizo 

(Leucophyllum frutescens)

Family:  Scrophulariaceae

When seen:  October 2019  

Exomalopsis birkmanni; (c) Copyright 2019 Paula Sharp

A female Exomalopsis birkmanni

Exomalopsis birkmanni; (c) Copyright 2019 Paula Sharp

A female Exomalopsis birkmanni

Exomaopsis birkmanni; Copyright 2019 Paula Sharp

A male Exomalopsis birkmanni

Exomalopsis Species of the Lower Rio Grande Valley

CITE THIS PAGE:  Sharp, Paula and Ross Eatman.  "Anthophorula and Exomalopsis."  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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