For These Spiders, "Size Does Matter"

Four newly discovered tarantula species were just dubbed the "Genital King," and for tarantulas, size really does matter.

The species are all under the genus Satyrex, which loosely translates to the epithet that Tinder dates around the world would love to boast. Still, they would certainly fall short compared with this tarantula, which can be found in southeastern Yemen and southwestern Oman, countries that share a border in Asia on the Arabian Peninsula.

A study published by the peer-reviewed scientific journal ZooKeys revealed the discovery of the well-endowed spiders.

Spiders don't have penises, but instead have pedipalps, which are secondary sexual organs that deliver sperm to females, said Alireza Zamani, the arachnologist and taxonomist at the University of Turku in Finland, who discovered the spider.

Most tarantulas' pedipalps are around 1.5 times larger than the carapace, their midsection, according to Zamani. It's "extremely rare," but sometimes pedipalps can be 2.5 times longer.

However, for the Genital King, "it is almost four times longer than the carapace," said Zamani. "It's almost as long as the longest legs of the tarantula."

If the tarantula swapped roles, and those proportions belonged to a human instead, their penis would almost be the length of their leg.

How did the spider develop such a big member? Well, researchers don't know, but they have a hypothesis.

"This elongation has happened as a result of what we call sexual selection," Zamani said. "The females of this species, and probably others that we are currently considering in this genus, are very, very aggressive."

The tarantulas are more aggressive than any species in the Americas.

So, the running theory is that the tarantulas have such long pedipalps because it makes it easier for them to administer their sperm into the female and make a quick getaway before the female tarantula can attack.