Tarantulas with massive penises have been discovered by scientists

'It seems that size really does matter.'

Tarantulas are large and hairy spiders — the largest of which have a leg span of around 30cm — that inhibit hot climates like rainforests and desserts.

The four new species have been found in both the Arabian Peninsula and the Horn of Africa.

The tarantulas’ palps — the scientific name for their reproductive appendage — were the largest ever recoded in the species.

The biggest of the lot, known as the satyrex ferox, has a palp that measures 5cm long.

While this may not seem giant to us, that 5cm length makes the palp, four times the length of the tarantula's head and almost as long as its longest legs.

The long palps give male tarantulas an evolutionary advantage.

They help the creepy crawlies to keep a good and safe distance away from females of the species while mating.

Females are known for being the more dangerous and aggressive members of the species, even to their partners.

The study clears this up, saying the long penises help to “facilitate copulation while minimising the risk of cannibalism, as it allows the male to position himself slightly away from the female rather than directly beneath her.

“This is plausible given the extremely aggressive defence behaviour observed in females of this genus.”

Dr Alireza Zamani of the University of Turku, who led the study, said: "The much longer palps of satyrex longimanus and the four newly described species were among the primary characters that led us to establish a new genus for these spiders, rather than place them in Monocentropus.

"So at least in tarantula taxonomy, it seems that size really does matter."