More than 70 Buddhist monks were hospitalized in northern Thailand on June 23 after being attacked by a giant swarm of bees, according to news reports. It was unclear what provoked the bees, which were from hives kept at the monks' temple and had never posed a threat previously.

Bees from several of the hives attacked the monks while they were sweeping the grounds of the Luang Worawihan temple in Chiang Mai province. Of the 76 monks who had to be rushed to the hospital with stings, 19 were in serious condition and six were in a coma, according to the Deccan Herald.

Temples often keep beehives, as the wax is useful for making candles.

Bees typically swarm in the late spring and early summer, when their numbers have grown to the point that half of them must break away from their hive and form a new colony elsewhere. The behavior is controlled by pheromones, or chemical signals, given off by the colony's queen.

Attacks are also escalated by pheromones. When a bee stings, it not only injects toxins into the victim, it also releases alarm pheromones. When these chemical signals are given off near a hive or swarm, they can trigger other bees to come to their colony mate's defense, often attacking until the victim flees or is killed.

When one person comes to another victim's aid, the bees will sometimes turn on the newcomer, according to the U.S. Department of Agriculture. In this way, bee attacks can escalate and spread.

Multiple bee stings can induce nausea, rashes and difficulty breathing. Large doses of the venom cause a sharp drop in blood pressure and can be fatal in humans, according to the USDA.

Follow Natalie Wolchover on Twitter @nattyover. Follow Life's Little Mysteries on Twitter @llmysteries. We're also on Facebook & Google+.

Related on Life's Little Mysteries:

This story is copyright 2012 Lifes Little Mysteries, a TechMediaNetwork company. All rights reserved.