The Pure Golden Green Sweat Bee (Augochlora pura)
By Beatriz Moisset and Vicki Wojcik, Pollinator Partnership Chequamegon-Nicolet National Forest
There are many sweat bees, or halictid bees, that visit wildflowers, native plants, and even crops. Augochlora pura does not have a common name, but it does not seem to need one with such a musical scientific designation that mean “pure golden green”. Like many metallic bees, Augochlora pura displays metallic tones that are usually bright green, but sometimes coppery or golden, and even a deep dark green that looks almost blue.
From the Canadian Rockies all the way though to Florida, this pure golden green bee can be busily visiting flowers from April to October. During warmer years, it can be seen as soon as February and as late as November in the northern and southern ends of its range.
Not a very choosy bee, it visits a wide range of flowers; many of them are members of the daisy family, Asteraceae, such as asters, goldenrods and coreopsis. Augocholra pura also visits members of the rose family (Rosaceae). Early in the season, it visits maple flowers. Although most maples are wind-pollinated, others carry a drop of glistening nectar very exposed on the center of their tiny flowers. Bees prize this nectar at a time when there are not many other good blooms and floral resources are scarce. Later on, it visits milkweeds, hydrangeas, spiderwort, verbena and others.
This wonderful little green bee has a lifestyle that distinguishes it from other halictid bees. Most nest in holes in the ground and a few others use hollow twigs, but Augochlora makes her nests under the loose bark of old trees. Where you see a fallen log on the forest floor female Augochlora see valuable real estate. She builds cells made of mud and debris found under the bark that she glues together. She works throughout the days gathering pollen from her favorite flowers, carrying it back to her log home on her hind legs. In her nest, she mixes the pollen with some nectar and her own saliva. Scientists think that her saliva has antiseptic qualities that help keep this food fresh and add extra protection to the eggs. Once she has gathered enough food for one larva she lays an egg inside the cell and seals it. Her nests are lined with an impermeable thin membrane that she produces from glands on her body. The nests need all this protection because there are marauding ants and many other little predators that would promptly devour her babies; bee larvae make delicious meals for hungry predators.
The larvae grow well-nourished under the shelter of the fallen log and bark. The larvae grow and develop until they reach full size during the summer. These baby bees will not come out quite yet, they go into a state of rest called pupation, and emerge later in the summer or in the fall. Fall is mating season for these bees. Once they the males die and the females remain lazily visiting flowers as late as November. These females are not gathering food for their families; they are building up fat to spend the winter in hibernation so that they can be ready in the spring once frost melts and the first blooms appear.
Next time you are in your garden keep an eye out for this common, yet wonderful little bee.