DARK SWEAT BEES OR FURROW BEES
Genera Halictus & Lassioglossum
Halictini -- small, nonaggressive "sweat bees," are a highly important group of native pollinators, instrumental in the propagation of an impressive range of commercial crops -- among them squash, legumes, sunflowers, watermelons, apples, berries, carrots, tomatoes and peppers, to name but a few. Sweat bees are also essential pollinators of Texas native flora and garden flowers.
This guide page features common sweat bees belonging to the genus Halictus and the genus Lasioglossum. Also known as "furrow bees," Halictus and Lasioglossum tend to be small to very small; are usually black, dark brown or dark-metallic; and often have pale bands of hair on their abdomens. Females usualy have dark faces and legs and carry pollen on scopae (sticky brushes) located on their hind legs. Males often have partly-yellow faces or legs.
Male ligated furrow bees (Halictus ligatus) - Photo credit Ernesto Herrera
Halictus and Lasioglossum furrow bees
Halictus are found throughout the world. There are 25 species in the Americas; of these, six have been documented in Texas: Halictus confusus, H. ligatus, H. parallelus, H. poeyi, H. rubicundus and H. tripartitus. All of these are dark brown or metallic bronze.
Halictus nest in the ground, in loose soils. Some Halictus are solitary, and others nest in semi-social groups that pass through multiple generations in a single summer. Halictus species of the Valley are broad generalist pollinators.
Lasioglossum is a much vaster genus than Halictus, represented by 280 species in North America, and by more than 150 species in Texas alone. Hairsplitting differences among Lasiglossum species make identification of individual types challenging. In his massive work The Bees of the World, the great entomologist Charles D. Michener dedicated twelve pages of fine print to the taxonomical traits of various Lassioglossum after describing them as "a genus of morphologically monotonously similar bees”.
Texas Lasioglossum are black, brown, or metallic gold or bronze. They usually have bands of pale hair on their abdomens; some have red abdomens. In the Lower Rio Grande Valley, the most commonly seen Lasioglossum are metallic bees belonging to the subgenus Dialictus.
Lasioglossum tend to be generalist pollinators, although some species specialize in pollinating particular plants. Lasioglossum females usually build nests in loose soils, consisting of single narrow shafts with series of branches. The bees secrete a waxlike substance used to line their brood cells. The behavioral habits of this broadly-defined genus vary widely by species: some Lasioglossum are solitary, but others form semi-social groups or colonies.
Lasioglossum vs. Halictus
Striped Lasioglossum sweat bees usually can be told from striped Halictus sweat bees by an examination of the bees' wings and the positioning of the bands girding the bees' abdomens.
As shown in the photo strip here, on striped Lasioglossum sweat bees, the pale hair bands on the bees' abdomens usually appear on the inner edge of each segment (the edge closer to the bee's head). Conversely, on Halictus sweat bees, the pale hair bands are on the outer rim of each abdominal segment (the edge closer to the abdomen's tip).
In addition, the veins on the outer edges of Halictus forewings tend to be boldly defined. By contrast, the outer forewing veins of some Lasioglossum are weakly-defined.
A metallic Lasioglossum (Dialictus) coactum
Traits of Halictus and Lasioglossum furrow bees
This is a female Halictus ligatus. In Texas, Halictus sweat bees are dark or dark-metallic with pale bands on their abdomens.
This is a male Halictus ligatus sweat bee. Halictus males often have partly-yellow legs. Note how the bands of hair on the abdomen hug the outer rims of each segment. This is a trait of Halictus generally.
Female Halictus sweat bees tend to have dark faces.
TAXONOMY OF FURROW BEES SHOWN HERE:
Halictus Sweat Bees
Species: Halictus (Odontalictus) ligatus
(Ligated sweat bee)
Lasioglossum Sweat Bees
Subgenus: Lasioglossum (Dalictus) coactum
(Constricted metallic bee)
Halictus & Lasioglossum Species of the National Butterfly Center & Lower Rio Grande Valley
Ligated furrow bee
aka Ligated sweat bee
Halictus (Odontalictus) ligatus
Size: 7-9 mm (male)
7-10 mm (female)
Associated plants at NBC:
Hierba del marrano
Plant family: Asteraceae
September - November 2018
April, October 2019
This is a female Halictus ligatus, commonly known as a ligated furrow bee: females have dark heads, bodies and legs. Their abdomens are striped with bands of pale hairs.
Face of a female ligated furrow bee. Females of this species have dark faces and jaws. Their antennae are dark and relatively short.
Larger females of this species tend to have disproportionately large heads, a trait that helps in identifying them.
A male ligated sweat bee: males have generally dark bodies and heads, dark abdomens striped with pale hairs, partly yellow faces and jaws and partly yellow legs.
Close-up of the face of a male Halictus ligatus. Note the yellow markings on the mandibles and clypeus.
The antennae of male ligated sweat bees are longer than those of their female counterparts. The male bee's antennal scapes and pedicels are dark; the antennae segments above these are golden on the front surfaces and brown behind.
A female Halictus ligatus
A male ligated sweat bee
Ligated sweat bees. Despite their small size, ligated sweat bees are key pollinators of commercial crops; they are among the four most important pollinators of commercial sunflowers.
At the NBC, if you look carefully at nearly any patch of composite flowers -- sunflowers, Mexican hat, resinbush, cowpen daisies, blanketflower or purple hierba del marrano -- you are likely to see several of these bees, often perched two or three to a blossom. In the Lower Rio Grande Valley, ligated sweat bees also visit a gamut of wildflowers of other plant families, among them, salvias, mallows, milkweeds, verbenas, ground cherry and willows.
Ligated furrow bees are black-eyed, dark-brown bees with white bands of hair on their abdomens, and clear wings with brown veins. Females have dark legs; dark faces and mandibles; and dark, medium-length antennae. Females often appear lugging hefty loads of pollen on their hind-leg scopal hairs.
Male ligated sweat bees have yellow legs with dark markings on them; partly-yellow faces; and mandibles that are yellow and reddish-brown. The males' antennae are long and mostly brown, with golden-yellow front surfaces.
Constricted metallic bee
Lasioglossum (Dialictus) coactum
Size: 4.5 - 5 mm (females and males)
Plant family: Euphorbiaceae
shrubby blue salvia
Plant family: Lamiaceae
red prickly poppy
Plant family: Papaveraceae
Plant family: Asteraceae
When and where seen:
Bahia Grande NWR
Laguna Atascosa NWR
Las Palomas Refuge
Lasioglossum (Dialictus) visit an array of flowers in the Valley. They are among the few native bees that gather pollen from prickly poppies, such as the Argemone sanguinea shown here.
A female Lasioglossum (Dialictus): bees of this subgenus are typically a metallic bronze, greenish-bronze or gold.
A female Lasioglossum (Dialictus) coactum. Bees of this species appear golden in direct sunlight and bronze in indirect light.
A female Lasioglossum coactum
A male Lasioglossum coactum
Lasioglossum (Dialictus) coactum. Metallic furrow bees of the Lasioglossum subgenus Dialictus can be very difficult to identify, in part because of their small size. Many furrow bees of this subgenus in the Valley remain uncatalogued.
Lasioglossum (Dialictus) coactum is one of the easier bees of its subgenus to identify. it can be recognized (under strong magnification) by its constricted first and second abdominal segments (T1 and T2); viewed from above or in profile, the segments' rims appear as if they had been pulled in tightly with a belt.
Lasioglossum (Dialictus) furrow bees engage in a wide range of behavior, from solitary to primitively eusocial. Some, but not all, solitary varieties form large aggregations. The bees’ nest structures range from the simple to the complex. Most Lasioglossum (Dialictus) nest in the ground; a minority nest in pre-existing cavities created by other insects in wood.
Lasioglossum (Dialictus) tend to be generalist pollinators that forage on a seemingly endless array of plants. In the Lower Rio Grande Valley, they are among a handful of bees that have been observed pollinating prickly poppies (Argemone).
CITE THIS PAGE: Sharp, Paula and Ross Eatman. "Halictus and Lasioglossum." Wild Bees of the National Butterfly Center of Mission, Texas. 15 Jan. 2019, http://www.wildbeestexas.com. Accessed [day/month/year guide accessed].