Reputation: Tarantulas are big. They are deadly. They attack humans. The female tarantula eats the male tarantula after sexual congress.

Reality: What we think of as tarantulas are not tarantulas. Most of the spiders we think of as tarantulas are small. They are rarely lethal. Post-coital cannibalism is rare.

The spiders we think of as tarantulas are not really tarantulas at all. In fact, the original tarantula is a relatively small, innocuous wolf spider. It lives in southern Europe, including around the city of Taranto in southern Italy, from which it gets its name.

They were probably being bitten by the local black widow

In bygone centuries, Lycosa tarantula had a fearsome reputation. Local peasants believed its bite to be lethal and came up with a novel antidote to its venom: a frenzied dance known as the Tarantella.

In fact, the Taranto tarantula is not dangerous at all and local peasants had failed to identify the species responsible for lethal bites. "They were probably being bitten by the local black widow," says Dave Clarke, head of invertebrates at London Zoo in the UK.

Nevertheless, the fear of the wolf spider from Taranto endured. So when European explorers began to encounter even bigger, hairier and more fearsome spiders on their travels to South America, they just called them tarantulas too.

The spiders we think of as tarantulas should, more properly, be called bird-eating spiders or Theraphosids. But, hey, let's just call them tarantulas, shall we?

The largest recorded specimen of Theraphosa blondi was the size of a dinner plate

The word tarantula conjures up an image of the Mexican red-kneed tarantula (Brachypelma smithi). But there are, in fact, around 650 different species of Theraphosid.

Most of these are pretty small, with a leg span of little more than 2cm.

However, the family is famous for its monsters, like the Goliath birdeater from northern South America. The largest recorded specimen of Theraphosa blondi was the size of a dinner plate, with a leg span of 28 cm. By mass, it's the largest spider in the world.

In popular culture, tarantulas are often depicted going on the offensive, as in the classic scene in the James Bond movie Dr No, where a tarantula emerges from beneath the bedclothes to feel its way across Sean Connery's naked chest.

The bite is normally no worse than a bee sting

In reality, this is not something that tarantulas do. "Most spiders can sense the heat from our bodies and will avoid us," says Clarke. "They are not naturally very aggressive."

When tarantulas are threatened by a predator "their first defense is always to hide and run away." If really cornered, they might use their fangs to deter a would-be assailant but they don't always bother to inject venom.

Even if they do use venom, it's rarely lethal. "The venom is used to subdue their prey," says Clarke. "None of them is normally lethal. The bite is normally no worse than a bee sting."

That said, cannibalism is probably a post-coital hazard for male tarantulas, as it is for many other species of spider.

Males always left swiftly after mating

"As the male attempted to uncouple and move away, the female followed and suddenly jumped on him," wrote researchers in a rare study of the sexual strategies of the North American desert blond tarantula. "It took her 6 min to subdue the male, after which time she dragged him back and into her burrow. We assume that ingestion occurred."

But this rather gruesome event only happened once in the course of the study, suggesting that males are alive to the danger. "Males always left swiftly after mating," noted the researchers. You would, wouldn't you?

"It is a hazard but it doesn't happen often," says Clarke.

That said, the staff at London Zoo overseeing the breeding of captive tarantulas are careful to take precautions. "We stand by with a ruler in case the female gets the wrong idea," says Clarke.