The different species of honey bees are distinguished from all other bee species (and virtually all other Hymenoptera) by the possession of small barbs on the sting, but these barbs are found only in the worker bees.
The sting apparatus, including the barbs, may have evolved specifically in response to predation by vertebrates, as the barbs do not usually function (and the sting apparatus does not detach) unless the sting is embedded in fleshy tissue.
While the sting can also penetrate the membranes between joints in the exoskeleton of other insects (and is used in fights between queens), in the case of Apis cerana japonica, defense against larger insects such as predatory wasps (e.g. Asian giant hornet) is usually performed by surrounding the intruder with a mass of defending worker bees, which vibrate their muscles vigorously to raise the temperature of the intruder to a lethal level (“balling”).
Previously, heat alone was thought to be responsible for killing intruding wasps, but recent experiments have demonstrated the increased temperature in combination with increased carbon dioxide levels within the ball produce the lethal effect.
Defense can vary based on the habitat of the bee.
In the case of those honey bee species with open combs (e.g., A. dorsata), would-be predators are given a warning signal that takes the form of a “Mexican wave” that spreads as a ripple across a layer of bees densely packed on the surface of the comb when a threat is perceived, and consists of bees momentarily arching their bodies and flicking their wings.
In cavity dwelling species such as Apis cerana, Apis mellifera, and Apis nigrocincta, entrances to these cavities are guarded and checked for intruders in incoming traffic.
Another act of defense against nest invaders, particularly wasps, is “body shaking,” a violent and pendulum like swaying of the abdomen, performed by worker bees.
The stings of honey bees are barbed and therefore embed themselves into the sting site, and the sting apparatus has its own musculature and ganglion which keep delivering venom even after detachment.
The gland which produces the alarm pheromone is also associated with the sting apparatus. The embedded stinger continues to emit additional alarm pheromone after it has torn loose; other defensive workers are thereby attracted to the sting site.
The worker dies after the sting becomes lodged and is subsequently torn loose from the bee’s abdomen. The honey bee’s venom, known as apitoxin, carries several active components, the most abundant of which is melittin, and the most biologically active are enzymes, particularly phospholipase A2.
Honey bee venom is under laboratory and clinical research for its potential properties and uses in reducing risks for adverse events from bee venom therapy, rheumatoid arthritis, and use as an immunotherapy for protection against allergies from insect stings.
Bee venom products are marketed in many countries, but, as of 2018, there are no approved clinical uses for these products which carry various warnings for potential allergic reactions.