Bearbees (クマハチ) are an animal species in the other world. They are born from eggs into caterpillars and then go through a cocoon phase before becoming full grown Bearbees.
A group of bearbees laid their eggs in the empty guest wing at Blood Pledge Castle and Yuuri and Wolfram went to investigate the monsters that were in the wing not knowing they were bearbees. They ended up getting stuck down with the caterpillars before they changed into the cocoon form. When the bearbees emerged from their cocoons they thought that Yuuri and Wolfram were their parents.
There is a high quality paint made from bearbee droppings.