Stingless bees have their nests protected by soldiers
(PHYSorg.com Biology)

Although stingless bees do not have a sting to fend off enemies, they are nonetheless able to defend their hives against attacks. Only four years ago it was discovered that a Brazilian bee species, the Jatai bee, has a soldier caste. The slightly larger fighters guard the entrance to the nest and grip intruders with their powerful mandibles in the event of an attack. Working in collaboration with Brazilian researchers at the University of Sao Paulo and Embrapa in Belém, biologists at Johannes Gutenberg University Mainz (JGU) managed to identify four further species which produce a special soldier caste to defend their nests. `This is therefore not a solitary case, as it seems there is an astounding variety of social organization among other stingless honey bees,` said Dr. Christoph Grüter of Mainz University. The scientists had examined a total of 28 different species from entirely different habitats in Brazil.