Sweat Bees: Tiny Metallic Bees That Land on Your Skin
Sweat bees are small native bees, often metallic green or dull black, that land on your skin to drink sweat for its salt and moisture. Only females can sting, and they usually do so only when pressed against the skin, for example when trapped under a sleeve or swatted; the sting is mild. They nest in the ground, are not aggressive, and are important pollinators. In most yards the right response is to brush them off gently and leave them alone.
Sweat bees are the family Halictidae, the second largest bee family. Washington State University puts the North American total at about 500 species. Most people meet them on a hot afternoon in the garden, when a tiny bee settles on a forearm and refuses to leave. That behaviour, not any threat, is what sends people searching.
What sweat bees look like
| Group | Size | Look | Notes |
|---|---|---|---|
| Lasioglossum and Halictus | About 2.5 to 10 mm | Black or dull metallic, slender | The ones that most often land on skin for sweat |
| Agapostemon (green metallic sweat bees) | Up to about 10 mm | Bright metallic green head and thorax, often a black and yellow striped abdomen | Fast fliers; females carry pollen on hairy hind legs |
| Augochlora and Augochlorella (all-green sweat bees) | Augochlora pura averages 8 mm | Shiny green all over, sometimes gold or blue | Augochlorella are the smallest and most abundant sweat bees in Missouri |
| Sphecodes (cuckoo bees) | Small | Black and red or orange, shiny, sparsely haired | Lay eggs in other bees’ nests and build none of their own |
Washington State University gives 0.1 to 0.4 inches (about 2.5 to 10 mm) for the common sweat bee genera Agapostemon, Halictus and Lasioglossum, and up to 0.8 inches for the family as a whole. UF/IFAS notes that about half of species are dull to metallic black and the rest metallic green, blue or purple, and that the family is identified by a strongly curved vein in the wing. The University of Michigan’s BioKIDS gives the pure green sweat bee an average length of 8 mm.
Sweat bees that are black
Many sweat bees are not green at all. NC State Extension describes Lasioglossum, a very diverse genus, as black or a dull metallic colour, with most species much smaller than a penny. A tiny, dark, slender bee lapping at your arm on a hot day is very likely one of these. They are easy to overlook as bees; Washington State notes many halictids do not look like bees and are often missed.
Do sweat bees sting or bite you?
They can sting, but rarely do, and they do not bite to feed. Only female bees and wasps can sting, because the stinger is a modified egg-laying organ, as Colorado State University and the University of Nebraska explain; male sweat bees cannot sting at all. The Missouri Department of Conservation says a gentle scrape will usually persuade a visiting sweat bee to move on, but pressing on a female may prompt a mild sting. In practice, stings usually follow a bee being pressed against the skin, trapped in clothing or slapped.
The sting is minor for most people. The CDC’s National Institute for Occupational Safety and Health notes that an insect sting may cause mild discomfort or pain, but that people allergic to venom may experience anaphylaxis, a potentially life-threatening reaction that requires immediate emergency care. Anyone with a known bee sting allergy, or who has trouble breathing or widespread swelling after a sting, should get medical help straight away.
What attracts sweat bees to you?
Salt and moisture. The Missouri Department of Conservation compares them to deer at a salt lick or an athlete with an electrolyte drink: they supplement a diet of nectar and pollen with salts from sweating humans. Washington State notes that Halictus and Lasioglossum in particular are attracted to human sweat, which they drink for the salt content. The University of Nebraska adds that some small species hover about and try to land on the skin to lap up sweat.
So the attractant is you on a hot day, especially when working or exercising outdoors. Yellowjackets and other wasps are drawn by different things, covered in our guide to what attracts wasps.
What is mistaken for sweat bees?
- Hover flies. The commonest mix-up. Hover flies are yellow and black bee mimics that also sip sweat, as University of Illinois Extension notes. They have two wings, bees have four, and they are shiny rather than fuzzy. Illinois Extension quotes the rule of thumb “two wings fun, four wings run”. Hover flies cannot sting, and their larvae eat aphids.
- Cuckoo wasps. Small metallic blue and green insects. The Missouri Department of Conservation says their bodies are covered in small pits that give a pebbly look, they can roll into a ball, and the females cannot sting.
- Yellowjackets. Larger, at 1/2 to 1 inch according to UC IPM, with jagged bright yellow and black stripes and a narrow waist. UC IPM advises preventing stings by removing the food sources that draw them. See our yellow jacket removal guide if that is what you have.
- Other ground-nesting bees. Mining bees and cellophane bees also nest in bare soil, many of them in spring. Our guide to ground bees covers how to tell them apart.
Where sweat bees live and nest
Nearly all sweat bees nest in the ground, and a few in rotten wood, according to the Missouri Department of Conservation. UF/IFAS says they typically nest in bare soil in a sunny location, and Washington State that they prefer loose, sandy soils. The University of Nebraska notes ground-nesting bees, including sweat bees, dig burrows in bare soil and in crevices in pavement and retaining walls, and illustrates halictid burrows in the gaps between paving bricks. UF/IFAS describes females digging nests and stocking each cell with pollen and nectar and a single egg.
Their social lives vary more than in almost any other bee family. UF/IFAS describes species that are solitary, communal, semi-social or fully social, and some that switch with season or location. The Missouri Department of Conservation describes a typical pattern: females that overwintered start nests in April, are joined by others, and by summer one egg-laying bee remains, with daughters as workers. Even the social Augochlorella rarely have more than a few occupants per nest, Missouri notes, and it explains that halictids, without a hive of sisters to defend, are not aggressive. That is the key difference from yellowjackets.
When sweat bees are about: what iNaturalist records show
We measured each group’s share of all US research-grade iNaturalist observations by month, which removes the summer rise in people recording. Sweat bees as a family peak in July at 233 on our index, more than twice their average share, with June at 178 and August at 185. They stay above average through September and October, at 132 and 127. Green metallic sweat bees, the Agapostemon genus, rise earlier and more steeply, reaching 234 in June and 231 in July, then hold above average into November at 110. Agapostemon accounts for about a quarter of all US sweat bee records, which reflects how eye-catching it is as much as how common.
The practical reading is that the sweat-on-your-arm season runs from June to early autumn, matching the hottest, sweatiest months, and that green sweat bees can still be about on warm days well into autumn.
Do sweat bees have a purpose?
Yes, a significant one. UF/IFAS calls them very important pollinators for many wildflowers and crops, including stone fruits, pome fruits, alfalfa and sunflower. The Missouri Department of Conservation notes that halictids are among the smallest bees that can buzz-pollinate, shaking pollen loose from flowers, and that about 30 per cent of US crops rely on native bees for pollination. Washington State describes the alkali bee, a halictid, as an important pollinator of alfalfa. The Missouri Department of Conservation also notes many native bee species are declining, which is a reason to tolerate sweat bees rather than treat for them. Our guide to pollinator protection and pesticides explains how insecticide use affects bees.
How do you get rid of sweat bees?
In most cases you do not need to, and extension services advise against spraying. What works is avoiding contact and, where needed, making a spot less inviting for nesting.
- Do not slap. The University of Nebraska advises backing off without slapping the bees and moving away if they hover to drink sweat. Slapping is what turns a visit into a sting.
- Brush, do not press. A gentle scrape usually moves a sweat bee on, the Missouri Department of Conservation says.
- Cover up on hot work days. Because sweat is the draw, long sleeves and wiping sweat off exposed skin reduce the number that land. This follows from what attracts them rather than from a trial.
- Change the soil if nests are in the wrong place. The University of Nebraska suggests planting turfgrass or a dense groundcover over bare areas to discourage ground-nesting bees, and avoiding nest sites if stinging is a concern. Nesting activity is seasonal, so a patch busy in summer is often quiet later.
- Leave insecticides out of it. Nebraska says insecticide treatment is rarely justified and limits it to cases where nesting interferes with imminent use of an area, such as an outdoor event. Washington State lists no chemical management for these bees.
Sweat bees are not a pest control job in the usual sense. If you are unsure whether ground nests belong to sweat bees or yellowjackets, which is a different matter, an identification from your county extension office or a licensed professional is worth having before anything is treated. Our bee removal cost guide covers the cases where removal genuinely makes sense, which mostly involve honey bees in walls.
Frequently asked questions
Do sweat bees sting or bite you?
Female sweat bees can sting, but they rarely do unless pressed against the skin, trapped in clothing or slapped, and the sting is mild for most people. Males cannot sting because the stinger is a modified egg-laying organ. Sweat bees do not bite to feed; they lap sweat for its salt. People with a known bee venom allergy should treat any sting seriously and seek medical help if symptoms spread.
What is mistaken for sweat bees?
Hover flies most often. They are yellow and black bee mimics that also sip sweat, but have two wings instead of four, look shiny rather than fuzzy, and cannot sting. Small metallic cuckoo wasps, which have pitted bodies and roll into a ball, are another lookalike. Yellowjackets are larger, at 1/2 to 1 inch, with jagged yellow and black stripes and a narrow waist.
How do you get rid of sweat bees?
Usually you do not need to. Brush them off gently rather than slapping, move away if several are landing, and cover skin on hot days. If they nest in bare soil where people gather, University of Nebraska Extension suggests planting turfgrass or dense groundcover to discourage nesting. Insecticide treatment is rarely justified, and sweat bees are valuable native pollinators.
Do sweat bees have a purpose?
Yes. Sweat bees pollinate many wildflowers and crops, including stone fruits, pome fruits, alfalfa and sunflower, according to UF/IFAS. Some are among the smallest bees able to buzz-pollinate. The Missouri Department of Conservation notes that about 30 per cent of US crops rely on native bees for pollination and that many native bee species are declining.
Sources
- UF/IFAS Extension, EENY-499, Sweat Bees, Halictid Bees, Halictidae, K. Buckley, C. Zettel Nalen and J. Ellis, 2011.
- Washington State University Hortsense, Halictidae: Alkali Bees, Sweat Bees and Cuckoo Bees, reviewed 2026.
- Missouri Department of Conservation, Field Guide: Halictid Bees (Sweat Bees).
- University of Nebraska Extension, EC3023, Bees and Wasps around the Home and Landscape, J. A. Kalisch, F. P. Baxendale, J. M. Green and S. T. Kamble, 2017.
- NC State Extension Pollinators, Ground Nesting Bees: What to Look for and What Species to Expect, H. Levenson, 2025.
- Colorado State University Extension, Taking the Sting out of Insect Encounters, Part 2, L. Mason, 2023.
- University of Illinois Extension, Hoverflies not sweat bees, K. Allsup, 2018.
- University of California Statewide IPM Program, Pest Notes: Yellowjackets and Other Social Wasps.
- University of Michigan BioKIDS, Augochlora pura, pure green sweat bee.
- Centers for Disease Control and Prevention, NIOSH, Insects and Scorpions at Work.
- The Pest Control Brief analysis of iNaturalist research-grade records, pulled October 2026.
