GREEN SWEAT BEES

Genus Augochloropsis, Augochlora & Augochlorella

Genus Agapostemon      

The sweat bee family, Halictidae, is a highly important group of wild pollinators.  Sweat bees are instrumental in the cultivation of an impressive range of commercial crops -- among them squash, legumes, sunflowers, watermelons, strawberries, tomatoes and peppers, to name but a few.  Sweat bees are also essential pollinators of both garden flowers and native flora, and are common visitors to wildflowers at the National Butterfly Center. 

Sweat bees span 14 genera within the United States and a seemingly endless plenitude of species. Some sweat bees are black or dark with striped abdomens.  Others -- members of the tribe Augochlorini and the genus Agapostemon -- are usually an eye-catching iridescent green.

Tribe Augochlorini:  Augochlora, Augochloropsis and Augochlorella 

Augochlora, Augochloropsis and Augochlorella sweat bees belong to the tribe Augochlorini.  Bees in this tribe are brilliantly colored -- they usually range from golden-green to an intense pure green to a dazzling blue-green.  Augochlorella and Augochlora sweat bees may be copper-colored or even metallic-pink as well. 

Augochlorini sweat bees tend to build nests in soil or, less commonly, in rotted wood.  Some form large aggregations in the ground, constructing nests in clumps linked together by earthen connections or rootlets. 

Augochlorini sweat bees sometimes act cooperatively, constructing nests that share a common entrance protected by a guard bee.   Some Augochlorini are capable of shifting between solitary and cooperative behavior, depending on environmental conditions.

Some Augochlorella and Augochlora sweat bees are considered to be “primitively eusocial.”  That is, they have a yearly life cycle split into spring and summer phases.  In the first spring “foundress phase,” the bees construct an underground nest and provision it for offspring.  When the young emerge, the males leave the nest, while the females remain in the nest  provisioning it for a second brood When this second brood hatches in late summer, the males and females mate. The males die and the inseminated females dig downward into the earth from the lowest parts of their nests.  They later emerge in spring to complete the colony’s life cycle.

Members of the tribe Augochlorini tend to be pollinator generalists.  At the National Butterfly Center, Augochlora, Augochloropsis and Augochlorella sweat bees visit the flowers of a wide and varied range of plant families.   The brilliant blue-green Aztec sweat bee (Augochlora azteca) alone appears to restrict itself principally to one plant -- alamo vine blossoms -- although this bee has been documented visiting the flowers of esperanza and prickly pear cactus as well.

Distinguishing among green sweat bee genera 

Augochlora, Augochloropsis and Augochlorella sweat bees can be distinguished easily from one another, and from bees of the genus Agapostemon, by minute traits that are obvious under a macro lens or microscope.  To the naked eye, bees of these four genera may be hard to tell from one another. 

Generally, Augochloropsis sweat bees tend to be somewhat larger than Augochlora and Augochlorella and are green or blue-green.  Augochlora at the National Butterfly Center may be green, golden-green, bluish-green or copper-colored.  NBC Augochlorella tend to be light-green, copper-colored or even a coppery-pink, like the one shown at right.

Here are two useful tips for distinguishing among green sweat bees genera.  (1)  First, examine the tegulae (the nodes where the bee's wings join its body).  The tegulae of an Augochloropsis are metallic-green and D-shaped.  The tegulae of an Augochlora are oval and brownish in color. The tegulae of Augochlorella are a pale reddish color and lack a distinctly oval shape.  (2) Second, if you have a macro lens, you can distinguish green sweat bee genera by examining the marginal cells in their forewings.  Differences in the wings of sweat bees are explained in more detail in the photo strip at bottom right.  This photo strip also shows other more subtle characteristics that distinguish green sweat bees of different genera.

Tribe Halictini:  Agapostemon 

Agapostemons are small-to-medium-sized, brilliantly-colored bees that look like flying emeralds.  To the naked eye, bees of the genus Agapostemon may resemble the iridescent bees of the Augochlorini tribe discussed above.  Nonetheless, differences in wing and leg structure, facial characteristics and DNA have led to the genus Agapostemon's placement in a different tribe known as the Halictini.  (This tribe also contains, among others, darkly-colored, dark-and-pale striped and and dully-metallic Halictus and Lasioglossum sweat bees; and parasitic Sphecodes bees.)

Agapostemons build nests in the ground.  Their nests consist of vertical tunnels, and are usually kept well-hidden under leaves or grass.  Like Augochlorini-tribe bees, Agapostemons are solitary, with each female provisioning her own nest , but the bees may act gregariously, building in close proximity with one another.  Like Augochlorini, Agapostemons sometimes share burrows whose entrances are watched by guard bees.

Agapostemon sweat bees tend to be larger than green Augochlorini-tribe sweat bees.  Agapostemon species also often show pronounced sexual dimorphism:  females may be an intense iridescent green all over, while males are only partly green, with striped yellow-and-dark abdomens, as exemplified by the Texas Agapostemon shown here.  In other species, such as the honey-tailed Agapostemon, also shown here, males and females both have striped abdomens, but detailed markings and coloration on the bees' legs, faces and abdomens differ.  

Agapostemons are usually generalist pollinators.  The honey-tailed Agapostemon visits plants as widely diverse as melons, cactus, cabbage, peas and mallows.  At the National Butterfly Center, this species is usually found in association with Berlandier's Fiddlewood and crucita.  Texas Agapostemons also pollinate plants from many different families.  At the NBC, they are usually spotted visiting sunflowers and other composite flowers of the aster family. 

Male Agapostemons of separate species are differentiated by such traits as the colors of their abdominal stripes; the markings on their hind legs; and the marks on the undersides of their abdomens (their sterna).

 

Female Agapostemon species can be difficult and sometimes impossible to tell apart with the naked eye.  In Texas, for example, the females of two species, Agapostemon angelica and Agapostemon texana, are morphologically identical; they can be told apart only if caught mating with males (which are more dissimilar) or through microscopic analysis or DNA testing.  Some female Agapostemons can be distinguished by wing color; or traits invisible to the naked eye, such as the colors of hairs on their legs; and the patterns formed by tiny pits and indentations on the bees' thoraxes.  These differences are illustrated in more detail in the photographs shown below of individual Agapostemon species.

TAXONOMY OF GREEN SWEAT BEES

Order:   Hymenoptera

Family:   Halictidae  (Sweat Bees)

Subfamily:   Halictinae

Tribe:   Augochlorini

Genus:  Augochlora, Augochloropsis, Augochlorella
NBC Species:   

    Augochlora azteca (Aztec sweat bee)
    Augochlora aurifera (Golden Augochlora)
    Augochloropsis metallica (Green metallic bee) 

    Augochlorella bracteata (Gilded Augochlorella)

Order:   Hymenoptera

Family:   Halictidae  (Sweat Bees)

Subfamily:   Halictinae

Tribe:  Halictini

Genus:   Agapostemon

NBC Species: 

    Agapostemon melliventris (Honey-tailed Agapostemon) 
    Agapostemon texanus (Texas Agapostemon)

 

Augochlora mellifera - (c) Copyright 2018 Paula Sharp

A female honey-tailed Agapostemon (Agapostemon melliventris)

Augochloropsis metallica green sweat bee - (c) Copyright 2018 Paula Sharp

A female green metallic bee (Augochloropsis metallica)

Augochlora azteca sweat bee- (c) Copyright 2019 Paula Sharp

A female Aztec sweat bee (Augochlora azteca)

A female Augochlorella

Agapostemon splendens sweat bee - (c) Copyright 2018 Paula Sharp

A female Agapostemon

AUGOCHLORA vs. AUGOCHLOROPSIS vs.
AUGOCHLORELLA vs. AGAPOSTEMON

Traits that help distinguish green sweat bee genera 

This photostrip summarizes basic differences among Augochlora, Augochlorella, Augochloropis and Agapostemon green sweat bees found within the United States.

AUGOCHLORA: An Augochlora's tegula (the node where the wing attaches to the bee's body) is dark and oval in shape. The bee's legs are dark and covered with fine, pale hairs.

A second view of the oval and dark tegula of an Augochlora bee. Augochlora are usually iridescent green overall, but sometimes may have coppery highlights.

The marginal cell of an Augochlora wing is truncate (lopped off at the tip, rather than pointed).

AUGOCHLORELLA: By contrast, the wing of an Augochlorella sweat bee has a pointed marginal cell (the cell to the left of the dark stigma in this picture).

Augochlorella sweat bees are usually light green. Sometimes, however, they are copper-colored or a metallic pink.

The tegula of an Augochlorella is often pale reddish in color.

AUGOCHLOROPSIS: The tegula of an Augochloropsis sweat bee is iridescent green and D-shaped.

Alternate view of the tegulae of an Augochloropsis.

AUGOCHLOROPSIS: The upper segments of an Augocochloropsis bee's legs are metallic green. The bee shown here is female.The lower segments of the female bee's legs are darkly-colored.

ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER

Mission, Texas

Green sweat bee, Augochlora azteca, Aztec sweat bee, Augochlora aurifera, Agapostemon melliventris, Agapostemon texana, Augochloropsis metallica

GREEN SWEAT BEES
Augochlora, Augochloropsis, Augochlorella & Agapostemon

Aztec Sweat Bee
Augochlora azteca

Family:  Halictidae

Size:  9 mm (female)

Food plants at NBC: 

 
Alamo vine 

(Merremia dissecta)
Plant Family:  
Convolvulaceae

Esperanza

(Tecoma stans)
Plant Family:  Bignoniaceae

Prickly Pear

(Opuntia  engelmannii)
Plant Family:  Cactaceae

When seen:

September & November 2018
April 2019 

A female Aztec sweat bee inside a yellow prickly pear blossom. Within the United States, this species is found only in south Texas. It also inhabits Mexico.

Dorsal view of bee

Face of a female Aztec sweat bee

Aztec sweat bee - Augochlora azteca - (c) Copyright 2019 Paula Sharp

A brilliant blue-green female Aztec sweat bee (female)

Augochlora azteca sweat bee - (c) Copyright 2019 Paula Sharp

A brilliant blue-green female Aztec sweat bee (female)

Golden Augochlora 
Augochlora (Oxystoglossella)
    aurifera

Family:  Halictidae

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

Food plants at NBC:  

Cowpen Daisy

(Verbesina encelioides)

Seaside goldenrod

(Solidago sempervirens)
Plant Family:  Asteraceae

Spiked Malvastrum

(Malvastrum americanum
   
var. Americanum)

Plant family:  Malvaceae

When seen:

November 2018, April 2019
October 2019 

The female Augochlora aurifera has reddish-brown jaws and legs, and bright reddish coloration on the joints between the bee's tibias and femurs.

Augochlora species are told apart by various factors including: size; general color; their geographic location; associated plants; and critical minute traits such as the appearance of the bee's propodeal triangle (a small area located at the back of the bee's thorax). This species, Augochlora aurifera, is smaller than the Augochlora azteca shown above, and has a generally gold coloration. At the NBC, Golden Augochloras favor aster-family flowers.

A male Augochlora aurifera

A male Auguchlora aurifera from above

A female Augochlora aurifera sweat bee; (c) Copyright 2018 Paula Sharp

A female golden Augochlora (Augochlora aurifera)

A male Augochlora aurifera sweat bee; (C) Copyright 2018 Paula Sharp

A male golden Augochlora (Augochlora aurifera)

Green Metallic Bee
Augochloropsis metallica

Family:  Halictidae

Size:  9 mm (male); 9 mm (female)

Food plants at NBC: 
 

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


Hierba del marrano

(Symphyotrichum sp.)
Plant Family:  Asteraceae

Erect Spiderling
(Boerhavia erecta)
Plant Family:  Nyctaginaceae

When seen:

September & November 2018  

A female Augochloropsis metallica. Note that the tegula (the node where the wing joins the body) is iridescent green.

The top segments of the Augochloropsis female bee's legs are iridescent green. The lower segments are dark and covered with white hairs, and the feet (tarsi) are reddish brown.

The female bee's abdomen has a narrow band of white hairs between the second and third segments.

A male Augochloropsis metallica: Note that the bottom halves of the male bee's legs are white, with sparse white hairs. The top halves are metallic green.

Close-up of the hind leg of a male Augochloropsis metallica

Dorsal view of male bee: Note the iridescent green tegulae (the nodes where the wings meet the body). This is a distinguishing trait of both male and female bees of the genus Augochloropsis.

Augochloropsis metallica sweat bee - (c) Copyright 2018 Paula Sharp

A female green metallic bee  (Augochloropsis metallica)

Augochloropsis metallica - (c) Copyright 2018 Paula Sharp

Close-up of a female green metallic bee  (Augochloropsis metallica)

Augochloropsis metallica - (c) Copyright 2018 Paula Sharp

A male green metallic bee  (Augochloropsis metallica):
Note the partly-white legs of  the male bee.

Green Metallic Sweat Bee Species of the National Butterfly Center

Gilded Augochlorella

Augochlorella bracteata

Family:  Apidae

Size:  6  (male)

Associated plant at NBC:  

Scorpion-tail

(Heliotropium angiospermum)
Family: Boraginaceae

When seen:  October 2019  

This male Augochlorella bracteata has a coppery-pink color when viewed with the naked eye. Bees of this species are often green or yellow-green.

Profile view of male Augochlorella bracteata.

Face of a male Auguchlorella bracteata: the bee's face is slightly wider than it is long, and is covered with fine white hairs. Part of the labrum is yellow. The clypeus is metallic, with the exception of two pale spots near the apical rim. The jaws are reddish.

Augochlorella bracteata sweat bee - (C) Copyright 2019 Paula Sharp

A male Augochlorella bracteata

Augochlorella bracteata sweat bee - (C) Copyright 2019 Paula Sharp

A male Augochlorella bracteata

Honey-tailed Agapostemon
Agapostemon melliventris

Family:  Halictidae

Size:  6 - 7 mm (male); 8-9 mm (female)

Food plant at NBC:  


Berlandier’s fiddlewood 

(Citharexylum berlandieri)

Pigeonberry
(Duranta erecta)

Plant Family:  Verbenaceae
 

Hierba del marrano

(Symphyotrichum sp.)
Crucita
(Chromolaena odorata)

Seaside goldenrod

(Solidago sempervirens)
Plant Family:  Asteraceae

 

When seen:

Sept. - Nov. 2018 - 2019

A female honey-tailed Agapostemon on Berlandier's fiddlewood blossoms. Both males and females of this species have green iridescent heads and thoraxes and striped yellow-and-brown abdomens.

Face of a female honey-tailed Agapostemon: the bee's yellow facial markings and antennae scapes are distinctive traits of females of this species. In most other Agapostemon species, females' faces are entirely green.

Head of a female honey-tailed agapostemon

A male Agapostemon melliventris: males are smaller and more slender than females, but have similar general coloring.

The stripes on the male bee's abdomen may be partly black and partly honey-colored.

A male honey-tailed Agapostemon on Berlandier's fiddlewood berries. Males often buzz around this plant looking for females, occasionally alighting to drink nectar from flowers.

Agapostemon melliventris; (C) Copyright 2018 Paula Sharp

A female honey-tailed Agapostemon  (Agapostemon melliventris)

Agapostemon melliventris; (C) Copyright 2018 Paula Sharp

A male honey-tailed Agapostemon (Agapostemon melliventris)

An Agapostemon melliventris sweat bee in the grips of an orb weaver spider - (c) Copyright 2018 Ross Eatman

A male honey-tailed Agapostemon in the grips of a spinybacked orb weaver spider

Associated plants at NBC: 

Crucita

(Chromolaena odorata)

Common sunflower
(Helianthus annuus)

Mexican hat
(Rabatida columnifera)

Family:  Asteraceae

Honey mesquite
(Prosopis glandulosa)

Family:  Fabaceae

 

When seen:

Feb. - Nov. 2018-2020

Texas Agapostemon
Agapostemon texanus

Family:  Halictidae

Size:  10 mm (male); 11 mm (female)

This is a female Agapostemon texanus, found mating with a male A. texanus. Because males of this species are easier to identify, the best way to ID a female is to surprise her with a male bee.

Female Texas Agapostemons are entirely green, with green abdomens -- unlike the males, which have black-and-yellow striped abdomens.

This is a male Texas Agapostemon. Male Texas Agapostemons have iridescent thoraxes and heads that are green or, less often, coppery-green like the one shown here. The male Texas Agapostemon has a yellow abdomen banded by dark stripes.

MaleTexas Agapostemons have yellow labrums and clypeuses (the parts between and above the jaws) and partially yellow jaws. The scapes and pedicels (bottom two segments) of their antennae are also yellow.

Agapostemon texanus - (c) Copyright 2018 Paula Sharp

A female Texas Agapostemon (Agapostemon texanus) 

Agapostemon texanus - (c) Copyright 2018 Paula Sharp

A male Texas Agapostemon (Agapostemon texanus)