Sweat bees, also referred to as halictid bees, (Halictidae) are so named for their habit of landing on people and licking the perspiration from the skin in order to obtain the salt. Bees in this family are common throughout North America, with over 1,000 species occurring in North and Central America.
Bees in this family are small to medium sized, ranging from 4 to 10 mm. They generally are black or brownish colored; however, there are species of sweat bees that are bright metallic green and some that have brassy yellow or red markings. Males tend to have yellow faces.
Sweat bees build nests in clay soil, sandy banks, and cavities in weeds or shrubs.
These are small to medium-sized bees that are often metallic in color. They may be solitary, semi-social, or highly social in their nesting and food-gathering habits. Sometimes, they are called "Sweat Bees," but this refers to the predilection of only a small number of species in this family (and some flies that resemble bees). Usually, they nest in the ground and line the brood cells with a water-resistant coating of chemicals. Three subfamilies and one tribe will be described, which vary considerably in their importance. Dufourinae (Dufourine Bees): There is some doubt whether this subfamily has been properly assigned to the Halictidae. There is only one species that appears in the database: Dufourea marginatus. It is not a common visitor of prairie wildflowers. Halictinae (Halictine Bees, Green Metallic Bees, etc.): There are many species in this subfamily, and they can be hard to tell apart. The Halictine bees are the among the most important and common visitors to prairie wildflowers, and have a long flight season. In appearance, these small bees may be black, dull brown, shiny green or blue, or have black and yellow stripes on the abdomen. The Agapostemon, Augochlora, and Augochloropsis spp., in particular, are called "Green Metallic Bees" because of their shiny appearance. The smaller prairie wildflowers are especially likely to be favored by these bees. Nomiinae (Alkali Bees): Alkali Bees are more common in the western United States. Only a single species, Nomia nortoni, is contained in the database from this subfamily. Alkali Bees typically nest in dry, open areas, and often have large hairy legs. Sphecodini (Cuckoo Halictid Bees): This tribe contains several Sphecodes spp. They are parasitic on the brood cells of other Halictid Bees.
Life History and Behavior
Sweat bees have a range of nesting habits, although all sweat bees are ground nesters. Some species have dispersed solitary nests; others are gregarious with densely situated nests and primitive social arrangements. Females dig branching burrows in loose soil. Each burrow ends in a single cell, in which the female deposits eggs and a pollen ball upon which larvae feed. Females mate before hibernating for the winter and begin nesting in early spring. Daughters are raised first, with males being raised in late summer or early autumn.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:13301
Specimens with Barcodes:10853
Species With Barcodes:1845
Relevance to Humans and Ecosystems
This family of bees engages in a behavior called sonication, or buzz pollination (see below). The bee places the anther in its jaw and vibrates each flower with its flight muscles, causing pollen to be dislodged. Wild blueberry (Vaccinium spp.)crops are more effectively pollinated through buzz pollination, and sweat bees do pollinate this plant. These bees visit between four and eight flowers per minute and carry significant pollen loads on their hind legs. Additionally, sweat bees are generalist feeders - they feed on, and subsequently pollinate, many different flower types. These behaviors and adaptations make sweat bees efficient pollinators. Examples of crops pollinated by sweat bees include blueberry (Vaccinium spp.), alfalfa (Medicago sativa), and watermelon (Citrullus lanatus). Other plants that benefit from sweat bee pollination include Brazilian orchids like Prescottia densiflora and Campylocentrum aromaticum , shadbush or serviceberry (Amelanchier spp.), moosewood, rhodora (Rhododendron, Subgenus: Pentanthera), and raspberry (Rubus spp.). One of the most well-known sweat bees is the alkali bee (Nomia melanderi), a great pollinator of alfalfa.
Sonication, or buzz pollination, is used by some types of bees (e.g., bumblebees, southeastern blueberry bee) to release pollen. The bees grab onto a flower and move their flight muscles rapidly. This causes the flower to vibrate and the pollen to become dislodged. Typically, buzz pollinated flowers have tubular anthers with an opening at only one end. The pollen grains are very small and not oily. Examples of buzz pollinated plants include members of the Solanaceae family (e.g., eggplants, potatoes, tomatoes)and some members of the genus Vaccinium (e.g., blueberries, cranberries). Buzz pollination occurs in about 8% of flowering plants worldwide.
The Halictidae are a very large and nearly cosmopolitan family of the order Hymenoptera consisting of small (> 4 mm) to midsize (> 8 mm) bees which are usually dark-colored and often metallic in appearance. Several species are all or partly green and a few are red; a number of them have yellow markings, especially the males, which commonly possess yellow faces, a pattern widespread among the various families of bees. They are commonly referred to as "sweat bees" (especially the smaller species), as they are often attracted to perspiration; when pinched, females can give a minor sting.
Most halictids nest in the ground, though a few nest in wood, and they mass-provision their young (a mass of pollen and nectar is formed inside a waterproof cell, an egg laid upon it, and the cell sealed off, so the larva is given all of its food at one time, as opposed to "progressive provisioning", where a larva is fed repeatedly as it grows, as in honey bees). All species are pollen feeders and may be important pollinators.
Many species in the subfamily Halictinae are eusocial at least in part, with fairly well-defined queen and worker castes (though not the same as the caste system in honey bees), and certain manifestations of their social behavior appear to be facultative in various lineages.
Several genera and species of halictids are cleptoparasites of other bees (mostly other halictids), and the behavior has evolved at least 9 times independently within the family. The most well-known and common are species in the genus Sphecodes, which are somewhat wasp-like in appearance (often shining black with blood-red abdomen- German: Blutbienen - usually 4-9 mm in body length); the female Sphecodes enters the cell with the provision mass, eats the host egg, and lays an egg of her own in its place.
Halictidae are one of the four bee families that contain some crepuscular species; these halictids are active only at dusk or in the early evening, so are technically considered "vespertine" (e.g. in the subgenus Sphecodogastra of Lasioglossum), or sometimes truly nocturnal (e.g. in the genus Megalopta). These bees, as is typical in such cases, have greatly enlarged ocelli. The other families with some crepuscular species are Andrenidae, Colletidae, and Apidae.
Systematics and evolution
The Halictidae belong to the hymenopteran superfamily Apoidea, series Anthophila. The oldest fossil record of Halictidae dates back to Early Eocene with a number of species, such as Neocorynura electra and Augochlora leptoloba known from amber deposits. Currently, the family is divided into four subfamilies, many genera and more than 2000 known species. The Rophitinae appear to be the sister group to the remaining three subfamilies (Nomiinae, Nomioidinae, Halictinae) based on both morphology and molecular data.
- Tribe Halictini
- Tribe unknown
- Pesenko, Yu. A. (1999). "Phylogeny and Classification of the family Halictidae Revised (Hymenoptera: Apoidea)". Journal of the Kansas Emtomological Society 72 (1): 104–123. Retrieved 15 September 2013.
- Engel, M.S., Archibald, S.B. An Early Eocene bee (Hymenoptera: Halictidae) from Quilchena, British Columbia. The Canadian Entomologist, Vol. 135, No. 1, 2003
- Engel, M.S. (1995). "Neocorynura electra, a New Fossil Bee Species from Dominican Amber (Hymenoptera:Halictidae)". Journal of the New York Entomological Society 103 (3): 317–323. JSTOR 25010174.
- Engel, M.S. (2000). "Classification of the bee tribe Augochlorini (Hymenoptera, Halictidae)". Bulletin of the American Museum of Natural History 250.
- Patiny, S. et al., Phylogenetic relationships and host-plant evolution within the basal clade of Halictidae (Hymenoptera, Apoidea). Cladistics 24 (2008) 255–269
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