SHARP-EATMAN
NATURE
PHOTOGRAPHY
STRIPED GREEN SWEAT BEES
Tribe Caenohalictini - Genus Agapostemon
Agapostemon are brilliantly-colored green bees that look like flying emeralds. To the naked eye, bees of the genus Agapostemon may resemble the iridescent green bees of the Augochlorini tribe discussed in this guide's nextsection. Nonethelss, differences in wing and leg structure, facial characteristics and evolutionary history have led to the genus Agapostemon's placement in a different tribe known as the Caenohalictini.
Traits of the Genus Agapostemon
Most Agapostemon are generalist pollinators that build nests in the ground. Their nests consist of vertical tunnels, and are usually kept well-hidden under leaves or other plant matter. Agapostemon are solitary, with each female provisioning her own nest, but the bees may act gregariously, building in close proximity with one another. Agapostemon sometimes share burrows whose entrances are watched by guard bees.
Agapostemon tend to be larger than most 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 (Agapostemon texanus). In other species, such as Tyler's agapostemon (Agapostemon tyleri) and the honey -tailed agapostemon (Agapostemon melliventris), males and females both have striped abdomens.
Male and female Agapostemon differ in other ways as well. Females usually have dark legs covered with short pale hairs, while males have predominantly yellow legs. Females' faces are frequently mostly green, while males have extensive yellow markings on their faces.
Differentating among Agapostemon species
Male Agapostemon species are differentiated by such traits as the colors of their abdominal bands; their facial characteristics; markings on their hind legs; and markings on the sternum (the underside of the abdomen).
Female Agapostemon species are usually told apart by such traits as the colors of their abdomens (whether they are entirely green vs. striped, and if striped, by the colors of the stripes); their facial characteristics; and wing color. In more challenging cases, females are distinguished by minute traits invisible to the naked eye, such as the colors of hairs on their legs; and the patterns formed by pits and indentations on the bees' thoraxes.
Females of some Agapostemon species can be difficult to identfy. In Texas, for example, females of the two species Agapostemon angelicus and Agapostemon texanus are morphologically identical. They can be told apart only through microscopic analysis or DNA testing -- or if they are caught mating with more easily identified males of their respective species.
A female honey-tailed Agapostemon (Agapostemon melliventris)
TRAITS OF AGAPOSTEMON
This is a female Agapostemon. In many Agapostemon species, the female is entirely green, without a banded abdomen. The legs of female Agapostemon are dark and hairy.
This is a male Agapostemon. Male Agapostemon have abdomens that are banded by pale or yellow stripes. This trait makes them easy to distinguish from green sweat bee genera such as Augochlora, Augochlorella and Augochloropsis.
The legs of male Agapostemon are usually predominantly yellow, with or without dark markings. Leg color helps identify both gender and species. This honey-tailed Agapostemon male has mostly-yellow legs.
A female Agapostemon texxanus: the faces of many female Agapostemon are nearly entirely iridescent green.
A male Texas Agapostemon: male Agapostemon tend to have yellow markings on their faces.
A female Agapostemon melliventris: in some (but relatively few) Agapostemon species, females also have yellow markings on their faces.
TAXONOMY OF STRIPED GREEN SWEAT BEES
OF THE LOWER RIO GRANDE VALLEY
Order: Hymenoptera
Family: Halictidae (Sweat Bees)
Subfamily: Halictinae
Tribe: Caenohalictini
Genus: Agapostemon
NBC Species:
Agapostemon melliventris (Honey-tailed Agapostemon)
Agapostemon texanus (Texas Agapostemon)
Agapostmeon typeri (Tyler's Agapostemon)
ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER
Mission, Texas
STRIPED GREEN SWEAT BEES
Agapostemon
Honey-tailed Agapostemon
Agapostemon melliventris
Family: Halictidae
Size: 6 - 7 mm (male); 8-9 mm (female)
Associated plants at NBC:
Berlandier’s fiddlewood
(Citharexylum berlandieri)
Golden dewdrops
(Duranta erecta)
Plant Family: Verbenaceae
Hierba del marrano
(Symphyotrichum sp.)
Crucita
(Chromolaena odorata)
Seaside goldenrod
(Solidago sempervirens)
Plant Family: Asteraceae
When seen at NBC:
Sept. - Nov. 2018 - 2019
A female honey-tailed Agapostemon on Berlandier's fiddlewood berries. Both males and females of this species have green iridescent heads and thoraxes and striped abdomens.
Most female honey-tailed Agapostemon have honey-brown abdomens striped with bands of white hairs.
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 many Agapostemon species, females' faces are nearly entirely green, or green and black.
A male Agapostemon melliventris: males are smaller and slenderer than females, but have similar general coloring.
The stripes on the male bee's abdomen are partly black and partly honey-colored. The male bee’s legs (including the hind legs) are mostly yellow. Dark spots on the hind legs are confined to the tip of the femur and base of the tibia.
Close-up of the male bee's abdomen. Note that the front face of the first segment (T1) is honey-colored - this trait helps distinguish male Agapostemon melliventris from other western Agapostemon species.
A female honey-tailed Agapostemon (Agapostemon melliventris)
A male honey-tailed Agapostemon (Agapostemon melliventris)
A male honey-tailed Agapostemon in the grips of a spinybacked orb weaver spider
Agapostemon melliventris is the predominant Agapostemon species of the Valley. It is common in Cameron, Hidalgo and Starr Counties. The distribution of Agapostemon melliventris is centered in the southwestern United States, Texas and northern Mexico. It ranges west to California and is found as far north as Montana and as far south as the Mexican state of Chiapas.
The male and female Agapostemon melliventris both have brilliant iridescent green heads and thoraxes, and striped abdomens. In the Valley, the female bee’s abdomen is usually honey-colored and striped with bands of short white hairs. (In other regions of the United States, the typical female's abdomen may be black.) The male’s abdomen is striped with narrow black and honey-colored bands; these bands are part of the integument (exoskeleton) and not formed by hairs.
The striped honey-brown abdomen and partly-yellow face of the female Agapostemon melliventris easily identify it in the Valley. Males usually can be recognized by their honey-brown stripes and predominantly yellow legs.
Associated plants at NBC:
Crucita
(Chromolaena odorata)
Common sunflower
(Helianthus annuus)
Mexican hat
(Ratibida columnifera)
Family: Asteraceae
Honey mesquite
(Prosopis glandulosa)
Family: Fabaceae
When seen at NBC:
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.
The female Agapostemon texanus is entirely green, with a green abdomen -- unlike the male, which has a black-and-yellow striped abdomen. Note that the female's legs are dark and covered with short pale hairs.
This is a male Agapostemon texanus. Males of this species have iridescent green (or coppery-green) thoraxes, and black abdomens banded by yellow stripes.
The male Agapostemon texanus has an ridescent green or coppery-green face. Yellow markings adorn the bee's labrum and clypeus (the parts between and above the jaws). Its jaws are partly yellow. The male bee's antennal scapes and pedicels are also yellow.
A female Texas Agapostemon (Agapostemon texanus)
A male Texas Agapostemon (Agapostemon texanus)
Agapostemon texanus is uncommon in the Lower Rio Grande Valley. Although it is a generalist pollinator, it is most likely to be found in the Valley in association with sunflowers and other large-flowered Asteraceae. This species is widespread throughout the United States, and ranges from Canada to Panama.
The female Agapostemon texanus is entirely iridescent green, without bands or pale facial markings. Males have black abdomens banded by yellow stripes.
Females are easily differentiated from Agapostemon tyleri and Agapostemon melliventris by their uniformly green coloring. Males are best identified by the black markings on their legs, as shown in the accompanying photo strip. Females cannot be differentiated with the naked eye from the nearly identifical female Agapostemon angelicus.
Agapostemon Species of the National Butterfly Center & Lower Rio Grande Valley
Tyler's Agapostemon
Agapostemon tyleri
Family: Halictidae
Size: 9-10 mm (female)
8-9 (male)
Associated plants:
Cenizo
Leucophyllum frutescens
Family: Scrophulariaceae
Texas olive
Cordia boissieri
Family: Acanthaceae
When and where seen:
June 17, 2021
Campos Viejo Ranch
Rio Grande City (Starr Co.)
The female Agapostemon tyleri has a black abdomen with bands formed by short white hairs.
Lateral view of a female Tyler's agapostemon
The female bee's face is iridescent green. A wide black band with a rounded median point rims the bottom edge of the clypeus. The female's mandibles are brownish, with black tips.
A female Tyler's agapostemon (Agapostemon tyleri)
A male Tyler's agapostemon
A male Agapostemon tyleri
Dorsal view of a male Agapostemon tyleri.
The male bee’s face is predominantly green. Its clypeus is rimmed with a yellow band with a sharp median point; its labrum and antennal scapes are also yellow, and its mandibles are mostly yellow with black tips.
Agapostemon tyleri is an uncommon species in the Valley. This species is found principally in high-altitude regions of Mexico and in desert areas of southern Arizona, New Mexico and west Texas. The bees shown here were found in Starr County, the westernmost county of the Lower Rio Grande Valley.
Both the male and female Agapostemon tyleri have iridescent green thoraxes and banded black abdomens. On females, the abdominal bands are formed by short white hairs. On males, the bands are pale yellow and part of the integument (exoskeleton) of the abdomen. Females’ legs are dark and covered with pale hairs; males legs’ are predominantly yellow, with some black markings on the upper segments. The female bee’s face is predominantly iridescent green, with a dark band rimming the bottom edge of the clypeus. The male bee's face is also iridescent green; its clypeus is rimmed with yellow.
The male bee can be best identified by these traits: the first yellow band on its abdomen is interrupted, and its sternum is entirely black. Traits that help differentiate the female Agapostemon tyleri from other South Texas Agapostemon include: its black-and-white striped abdomen, the lack of yellow on its clypeus, its size, its dark tegulae and its light-colored, transparent wings.
CITE THIS PAGE: Sharp, Paula and Ross Eatman. "Agapostemon." Wild Bees of the National Butterfly Center of Mission, Texas. 15 Jan. 2019, http://www.wildbeestexas.com. Accessed [day/month/year guide accessed].