Sweat bees (family Halictidae) are small, often metallic-colored native pollinators found across the globe. They pollinate a wide range of wildflowers and important crops, playing a significant role in agricultural and natural ecosystems. Measuring typically between 3 to 10 millimeters, they are among the most common bees in the Northern Hemisphere.
The Primary Attraction: Salt and Minerals
The common name “sweat bee” derives from the insect’s attraction to the perspiration of animals, including humans. This behavior, known as “lapping,” serves a specific physiological purpose: sweat contains sodium and other trace minerals the bees seek. These minerals are not a source of food energy, but a necessary dietary supplement.
Female sweat bees require these minerals, especially sodium, for successful egg production and reproductive fitness. Human sweat provides a highly concentrated and easily accessible source of these electrolytes. When a sweat bee lands on exposed skin, it is attempting to drink the mineral-rich moisture. This behavior is non-aggressive and rarely results in a sting unless the bee is swatted or accidentally crushed.
Floral Preferences and Color Cues
Beyond mineral requirements, sweat bees seek nectar for energy and pollen for protein to provision their nests. They are largely generalist foragers, visiting a wide variety of plants. However, their short tongues influence the types of flowers they can access, leading them to prefer open-architecture blooms where nectar and pollen are easily reachable.
Many species are highly attracted to flowers in the yellow, white, and violet color spectrums. Bees perceive color differently than humans, seeing in the ultraviolet (UV) range. Flowers often display UV patterns, known as nectar guides, which direct the bee toward the pollen and nectar source. These bees commonly forage on broad, accessible blooms like those in the Aster family, such as asters, sunflowers, and goldenrods.
Essential Habitat and Nesting Requirements
The long-term presence of sweat bees depends on suitable nesting sites, as approximately 70% of native bee species are ground-nesters. Sweat bees excavate tunnels in the soil, creating individual chambers for their offspring. They typically require bare, well-drained soil that is firm and unmulched, often preferring sunny locations like south-facing slopes.
These bees line their brood cells with a waxy substance to protect developing larvae from moisture and pathogens. While most species are solitary, they often nest in dense aggregations in the same patch of suitable ground. Undisturbed bare soil remains the primary habitat requirement for the vast majority of Halictidae, though a few species choose alternative sites like pithy stems or rotting wood.
Managing Interactions: Encouraging or Deterring Sweat Bees
To support sweat bee populations, providing both food and nesting resources is necessary. To encourage foraging, plant a diverse array of native flowers, such as yarrow, bee balm (Monarda species), asters, and sunflowers, ensuring continuous blooms from spring through fall. Providing a shallow water source with small pebbles or moss also offers a safe place for them to drink during dry periods.
Nesting habitat can be created by leaving small, undisturbed patches of bare soil exposed to sunlight, avoiding tilling or pesticide application. Some species are attracted to ground that includes a sparse surface mulch of small pebbles or cobbles. Allowing a section of lawn or garden edge to remain un-mulched provides the firm, stable ground they need for their tunnel nests.
If the goal is to deter their presence on a person, the strategy involves managing the primary attractant: sweat. Wiping down exposed skin to remove perspiration, or wearing light-colored, long-sleeved clothing, minimizes the appeal of a person as a source of salt and minerals. If a bee lands on the skin, remain calm and gently brush it away, as they are not inclined to sting unless trapped or accidentally compressed.