Bonus TIL: Primitive Eusociality!

One more TIL for the day, because I just learned it after posting my TIL and it's really cool: The Japanese carpenter bee Ceratina flavipes is probably at one of the very earliest stages of eusociality. Most of them are completely solitary and build solitary nests, but one in a thousand female Ceratina flavipes bees pairs with another female Ceratina flavipes bee and builds a joint nest. When they pair, they divide labor much like a eusocial insect -- one bee lays eggs and guards the nest, while the other forages for food. I'm not sure what the foraging bee gets from this relationship... perhaps this only happens in sisters? Or maybe they used to be more eusocial, and this is an occasional misfiring that brings back the old instincts.