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I was examining this very rotten stump for fungi when I noticed these small, metallic green sweat bees nesting in the wood. They looked like tiny, living emeralds. They had brilliant green heads, thoraxes, and abdomens that were covered with small white hairs. I identified these bees based on inspection of two distinguishing traits: (1) dark, oval shaped tegulae, and (2) the bee's faces had distinctive epistomal lobes where the parocular area extends down into the clypeus. I'm assuming the bees I spotted are mated females that are making nests in the wood.
I spotted several of these solitary sweat bees nesting in a rotting stump in a deciduous forest.
These bees are referred to as "sweat bees" because they like to lick sweat from human skin, most likely seeking salt. Electrolytes such as sodium are important for nerve and muscle function, in addition to a variety of other life processes. So, it appears that sweat bees imbibe human sweat in order to help them maintain homeostasis. Interestingly, as you can see in these photos, these bees are cobbling their nests together using galleries in the wood that were probably made by other insects. Within these galleries, the female bees will leave cakes made of pollen, nectar, and spit, which will soon be food for her offspring. It's thought that her saliva is added to the cakes because it has antiseptic qualities that help keep the food fresh and add extra protection to the eggs. After a brief interlude with a mate, she will lay eggs on the pollen/nectar balls. The nests are lined with a thin, impermeable membrane that she produces from glands in her body. The nests need this added protection because there are many predators that would gladly devour her offspring. When the larvae hatch, they consume the nutritious cakes. Once larval development is complete, they will pupate, and then emerge later as adults.
Spotted on Oct 23, 2017
Submitted on Oct 24, 2017
and 13 other people favorited this spotting