There is an interesting taster article (and ensuing discussion) on a new caste of soldier bees in a stingless bee of South America – the Jatai bee (Tetragonisca angustula).
The study, published in the journal Proceedings of the National Academy of Sciences, found that Jatai soldiers are 30% heavier than their forager nestmates, have larger legs and relatively smaller heads.
Whats interesting is that this is the first known incidence of a soldier caste in bees – ants and other super-organism species have specialist solder castes but it had yet to be seen in bees.
Evolution is a wonderful (in the true sense of the word) phenomenon.
In the honey bee (in our hives – Apis melifera), the role of hive protection is undertaken by the worker bees who will sting intruders as a form of defense, and alarmed bees will release a pheromone that stimulates an attack response in other bees. Some honey bees species also use a ‘mob’ tactic where they crowd around an intruder (particularly wasps) in a ball. The ensuing heat and, possibly, carbon dioxide kill the intruder. They also use this ‘ball of bees’ tactic to starve/kill a queen to be superseded.
Further Links (based on Wikipedia):
C. H. Thawley. “Heat tolerance as a weapon”.
Michio Sugahara & Fumio Sakamoto (2009). “Heat and carbon dioxide generated by honeybees jointly act to kill hornets”. Naturwissenschaften 96 (9): 1133–6.
Victora Gill (July 3, 2009). “Honeybee mobs overpower hornets”. BBC News.