~ Profiles of Pollinators & Backyard Wildlife ~
The bicolored sweat bee (Agapostemon virescens) is a common native bee throughout much of the U.S. It is fairly easy to recognize because its head and thorax are metallic green and its abdomen is striped (usually). White and black stripes mean it’s a female, while yellow and black stripes mean it’s a male. However, some females can have a solid green abdomen.
Although it is commonly called the bicolored sweat bee, and the genus Agapostemon is referred to as the metallic green sweat bees, none of these bees are attracted to human sweat. These “sweat bees” are no more likely than a bumble bee to land on you. Instead, the bicolored sweat bee can be found foraging on a variety of different types of flowers. It is considered a short-tongued bee which means it is going to be found most often on flowers with very short tubes so that it can reach the nectar. I commonly find it on flowers in the in the aster family, such as coneflowers, sunflowers, asters, goldenrods, etc.
The bicolored sweat bee is a solitary ground nesting bee. Each spring the female will dig a tunnel in an open patch of ground. Off the tunnel will be several branches. After building her nest, the female will gather pollen, take it back to her nest, form it into a ball with a little nectar and place it in one of the branches before laying an egg and sealing off that branch so each egg will have its own “room.”
Although it is a solitary bee, the bicolored sweat bee will sometimes nest communally. In these cases, several females may share the same entrance tunnel but then build individual branches off the shared tunnel with each of those branches having additional branches for the female’s eggs. In many ways, this is similar to our apartment buildings where multiple families share the same entrance but the building itself is divided into multiple individual homes.
Once the egg hatches, the larva will eat the ball of pollen that its mother left for it. According to a study done in New York, several generations of bicolored sweat bees may emerge during a single summer. Some of the females from the summer’s last generation will emerge to mate and forage before re-entering the nesting chamber to overwinter as an adult. The following spring they will build their nesting chambers and begin laying eggs.
Even though the bicolored sweat bee is a common native bee, there are gaps in our knowledge about this small bee. Much of what we know about its biology and life history is general to all or most species in the Agapostemon genus. Growing up, I used to think that you had to go someplace far away that was remote and exotic in order to study cool wildlife or discover anything new. I believed that we already knew everything about the critters in our backyards, especially the common stuff. The bicolored sweat bee is just one of many examples of how incredibly wrong I was.
Shannon Trimboli is a beekeeper, farmer, wildlife biologist, and author. She owns Grassy Roads Farm and Busy Bee Nursery & Consulting. Busy Bee Nursery & Consulting specializes in plants and habitat consulting services for honey bees, native pollinators, and wildlife conservation. In 2018, her first book, Plants Honey Bees Use in the Ohio and Tennessee Valleys, was published. Shannon also writes a weekly blog called Kentucky Pollinators and Backyard Wildlife. The blog features profiles of pollinators and wildlife, tips for attracting pollinators and wildlife, highlights of different plants for pollinators and wildlife, and life on the farm and nursery. You can sign up to have her blog emailed to you.