Reputation: Killer bees are huge and are equipped with lethal venom

Reality: Killer bees are actually smaller than regular honeybees. Their venom is also less powerful. They are aggressive, but not in Puerto Rico

The story of the killer bee reads like science fiction.

The Africanized honey bee is slightly smaller than its European cousin, so it actually carries less venom

In 1956, a Brazilian scientist called Warwick Kerr imported African honeybees to South America with the intention of breeding a more productive strain. Some of them escaped and bred with European honeybees in the wild, giving rise to a hybrid species.

These Africanized honeybees began to spread. By 1985, they had made it as far as Mexico. In 2014, researchers studying the spread of these hybrids across California found they had reached San Francisco.

Early in this invasion, the Africanized honey bees acquired the nickname "killer bees", inspiring plenty of fear and a rash of second-rate bee-related movies along the way.

The truth about killer bees is not quite what these films would have us believe.

For a start, the Africanized honey bee is slightly smaller than its European cousin, so it actually carries less venom. This venom is no more potent either so, bee for bee, the killer bee is the lesser threat.

The term gives the impression that these bees are out to kill, when they are actually defending their hive

The danger comes from the way these bees defend a hive. "Africanized bees respond to colony disturbance more quickly, in greater numbers, and with more stinging," researchers concluded in 1982. This finding has been replicated in several subsequent studies.

This aggressive response helps explain why Africanized honey bees have caused the death of several hundred people over the last 50 years.

In the absence of an allergic reaction, it would take around 1000 bee stings to deliver a lethal dose of toxin to an average-sized adult. European bees are rarely this combative. Africanized bees can be.

Nevertheless, referring to them as "killer bees" is misleading, says Bert Rivera-Marchand, an entomologist at the Interamerican University of Puerto Rico in Bayamón.

The Puerto Rican bees are slower to sting, and do so less frequently

"The term gives the impression that these bees are out to kill, when they are actually defending their hive," says Rivera-Marchand. "Regardless of how defensive a hive may be, foraging bees in the field do not attack and there is no aggression seen during swarming events."

Furthermore, Rivera-Marchand has found that Africanized honey bees on Puerto Rico, where they were first detected in 1994, show significantly reduced defensive behaviour.

In a paper published in 2012, he and his colleagues demonstrated that the Puerto Rican bees are slower to sting, and do so less frequently, than Africanized honeybees on the continent. The Puerto Rican killer bees behaved almost exactly like European honeybees.

The genetic makeup of these "gentle" bees bears an unmistakable Africanized stamp. Yet somehow, in less than 20 years, they have lost the extreme defensiveness that we have come to expect of killer bees. "The Puerto Rico beekeepers are using local Africanized bees for in their industry and do not report problems with highly defensive behaviour," says Rivera-Marchand.