On the hill between the Big Maple and the Herb & Butterfly Garden there are several small colonies of bees. I happened by one day when kids from our Wild Discoveries Day Camp were gathered around the entrance holes watching them stick their heads out, then pull back. They convinced me to try my little camera’s video mode:
Here is a bit of information about “Halictid Bees” I found by surfing the net:
Halictid Bees are small bees (1/4″ – 1/2″ long) in the family Halictidae. Most halictid bees are shiny black, metallic green, or metallic blue. Some halictid bees are called “sweat bees” because they land on skin to gather sweat droplets. The bees will sometimes sting while they are doing this, but only if they are swatted or startled. Some bee-like hover flies in the family Syrphidae are also sometimes called “sweat bees,” but they are not bees and do not sting or bite.
Most halictid bees are solitary and create underground nests for their offspring. However, halictid bees are especially interesting to biologists because many species have evolved to live in social colonies recently in evolutionary history. Closely related halictid bee species are known to be social in one habitat and solitary in another. These patterns can help biologists study the origins of social behavior among insects. Some Kentucky halictid bee species show intermediate social behavior: several individual bees create nests near one another but do not work together. – University of Kentucky
According to several websites, there are over 500 species of Halictidae in North America. They are important pollinators, especially with the mysterious failure of honey bee hives in recent years.