The side effects of a bite from a Brazilian Wandering Spider include tremors, difficulty breathing, copious amounts of salivation – and a long-lasting erection.

Scientists believe that harvesting PnTx2-6, which is present in spider venom, can create a natural Viagra that takes 20 minutes to become effective.

To find out how PnTx2-6 works, scientists cut off the penis of a dead mouse and connected it to an electrical stimulator, according to a Wired report.

University of Wisconsin researchers measured the contraction of the tissue muscles when they came into contact with different chemicals. The scientists found that the venom was effective and had fewer side effects compared with other erectile dysfunction drugs such as Viagra, which can cause nausea, back pain and blurred vision.

"The venom of the Phoneutria nigriventer spider is a very rich mixture of several molecules," said Dr Kenia Nunes, a physiologist at the University of Wisconsin.

"These molecules are called toxins, and then we have various toxins in this venom with different activity.

"Because of this, when a human is bitten by this spider, we can observe many different symptoms including priapism, a condition in which the penis is continually erect."

Researchers have now successfully recreated the PnTx2-6 gene and introduced it into a culture of caterpillar cells which produced the spider toxin.

Although there are a growing number of erectile dysfunction drugs on the market, they are ineffective for around 30% of men who take them.

The Brazilian wandering spider appeared in Guinness World Records from 2010 as the world's most venomous spider. The venom of the spider causes priapism in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence.