Lasioglossum sweat bees are common pollinators in agricultural landscapes. These bees are small black, brown, or iridescent green/blue bees that belong to the family Halictidae. They can often be mistaken for flies due to their small size and nondescript appearance compared to other bees. These bees are historically overlooked as important pollinators for crops compared to other bees, such as honeybees or bumblebees. It was originally thought that because of their small size, Lasioglossum sweat bees could not be as effective as these other bees at pollinating crops. However, due to their high abundance and the amount of time they spend on individual flowers, these sweat bees are just as, if not more effective, as pollinators. Further, Lasioglossum sweat bees exhibit buzz pollination, like bumblebees, which is necessary for successful fruit set in some crops, like those in the genus Solanum (tomato, eggplant, peppers). Fun Fact: Sweat bees are one of the most common and abundant pollinators in Indiana Watermelon!
Lasioglossum bees exhibit a range of social behavior, from solitary to varying levels of eusociality between species. After overwintering, females emerge from nests in the spring in search of males. Sweat bees are polyandrous, meaning the females mate with multiple males throughout the warm seasons. These females will then make new nests to rear their broods. Sweat bees are ground nesting, like bumblebees. Nests consist of brood cells for rearing larvae connected by a series of tunnels. These tunnels are important for soil aeration, which benefits crop production. Some species exhibit parasitic behavior, entering other species’ nests and laying their own eggs in existing brood cells. The parasite larvae then hatch and consume the original bee larvae that is present.
Agricultural landscapes are degraded habitats for many wild bee species, including Lasioglossum, and many traditional agricultural practices can have negative impacts on populations of these bees. Planting monocultures of single crop species can stress populations of sweat bees because these crops lack diverse floral resources and often produce a single mass flowering event in which bees must maximize their foraging activity. Excessive tillage can also harm these sweat bees by destroying their nests. Planting a diverse array of crops and adopting reduced tillage practices can offset some of these negative impacts. You can also help support Lasioglossum populations by planting plots of native, flowering plant species adjacent to crop fields. These plots are often called flower strips or pollination reservoirs, and they provide supplemental foraging habitat for the sweat bees, along with many other insects. You can contact your local native plant nursery to see which plants native to your area best support native pollinating insects, and some may offer premade seed mixes for purchase.
Be on the lookout for these wonderful little pollinators on your own farms or gardens. They are likely offering more pollination services than you realize! Check out our newest Pollination Series publication to learn more about this and other native bees in Indiana Specialty Crops POL-12.
Figure 1. Lasioglossum (subgenus Dialictus) sweat bee photographed under a microscope (Photo by Robert Grosdidier).
Figure 2. Lasioglossum sweat bee foraging on blackberry (Photo by Robert Grosdidier).