Sweat bees are a widespread and diverse group of insects commonly found across various environments, from urban gardens to natural landscapes. These small bees are often overlooked due to their size, yet they represent a significant portion of the global bee population. They exhibit a surprising range of appearances and behaviors.
Defining Sweat Bees
Sweat bees belong to the scientific family Halictidae, the second-largest bee family globally, with nearly 4,500 species. Often called “halictids,” their name derives from this family classification. This large family is found on every continent except Antarctica, with over 500 species native to North America.
Their common name, “sweat bee,” originates from their attraction to human perspiration. These bees seek out salts and moisture in sweat to supplement their diet of nectar and pollen. This behavior leads to frequent encounters with humans during outdoor activities.
Appearance and Identification
Sweat bees are small to medium-sized, typically 3 to 10 millimeters long, making them smaller than a honeybee. While many species are black or brown, a distinguishing characteristic is their metallic coloration, which can include iridescent shades of green, blue, copper, or purple. Some species, like the bicolored striped sweat bee, feature a metallic green head and thorax with a black-and-white striped abdomen.
Identifying a sweat bee involves observing their size, color, and specific physical traits. Many have a strongly curved basal vein in their wings and short tongues compared to other bee types. Though they possess body hairs, these are less dense than those on bumblebees or honeybees.
Ecological Contributions and Behaviors
Sweat bees are important pollinators for a wide variety of plants, including native wildflowers and agricultural crops like alfalfa, apples, sunflowers, and watermelons. Their small size allows them to access pollen in flowers larger bees might miss. Some species are also capable of “buzz pollination,” a technique that releases pollen from certain flowers like tomatoes and blueberries.
Their social structures are diverse, ranging from solitary species where each female builds and provisions her own nest, to communal or primitively social species where multiple females may share a nest entrance. Most sweat bees build nests underground, often in areas with sparse vegetation like bare soil or sandy patches. Some species also nest in rotting wood.
Interactions with Humans
Sweat bees are known for their attraction to human perspiration, landing on skin to collect salts and moisture. Despite this interaction, sweat bees are not aggressive. They sting only if threatened, such as when accidentally swatted, pressed against the skin, or if their nest is disturbed.
The sting of a sweat bee is mild, less painful than other bee stings, causing minor, temporary irritation, redness, or itching. However, as with any bee sting, severe allergic reactions are possible for sensitive individuals, though uncommon. If a sweat bee lands on you, gently brushing it away or remaining still can prevent a sting.